Part IA - Coast Colleges Home Page TSUNAMI.docx · Web viewPart III-G – Tsunami A.California Tsunami Threat3 Causes of a Tsunami4 Current Tsunami Hazard Mitigation Efforts in California5

Part III-G – Tsunami

A. CALIFORNIA TSUNAMI THREAT.................................................................................3CAUSES OF A TSUNAMI...........................................................................................4CURRENT TSUNAMI HAZARD MITIGATION EFFORTS IN CALIFORNIA...........................5Figure 1 - Tsunami Inundation Map, 2009.........................................................................................6

COASTAL FLOODING, EROSION AND SEA LEVEL RISE..............................................7EARTHQUAKES AND TSUNAMIS................................................................................8TSUNAMI CHARACTERISTICS....................................................................................9TYPES OF TSUNAMIS.............................................................................................10TSUNAMI AS A THREAT TO SOUTHERN CALIFORNIA................................................12HISTORY OF REGIONAL TSUNAMIS.........................................................................12Figure 2 - Maximum Run up -- Water Height above Sea Level in meters.......................................13

TSUNAMI HAZARD ASSESSMENT............................................................................13Figure 3 - Tsunami Run Up Map for Orange County.......................................................................15

TSUNAMI WATCHES AND WARNINGS......................................................................16COMMUNITY TSUNAMI ISSUES................................................................................17

B. HAZUS................................................................................................................19Table 1 - Orange County General Building Stock...........................................................................19Table 2 - Orange County General Building Stock Damage............................................................20

DEBRIS GENERATION............................................................................................21SHELTER REQUIREMENTS......................................................................................21ECONOMIC LOSS...................................................................................................21Table 3 - Building-Related Economic Loss Estimates....................................................................22Table 4 - Summary of Impacts on OC for Tsunami........................................................................22Table 5 - Summary of Impacts Orange County Essential Facilities................................................23Table 6 - Orange County School Districts - ASCIP provided Site-Specific Data............................23

TSUNAMI COASTAL FLOOD....................................................................................24Figure 4 - Orange County Tsunami Inundation Areas.....................................................................24

REGIONAL IMPACTS...............................................................................................25Table 7 - Summary of Impacts for Orange County due to a Tsunami............................................25Figure 5 – OC Total Direct Economic Loss resulting from Tsunami Flood Scenario.......................25

ESSENTIAL FACILITY IMPACTS...............................................................................26Table 8 - Orange County Essential Facility Loss Estimates – Tsunami Flood Scenario................27

C. CCCD TSUNAMI DAMAGE ESTIMATES...................................................................27Table 9 - List of CCCD Sites and Vulnerability Rankings for Tsunami...........................................28Table 10 - CCCD Tsunami Damage Estimates by Site..................................................................29

EARTHQUAKE AND CCCD DEVELOPMENT TRENDS................................................30D. CCCD TSUNAMI MITIGATION STRATEGIES.............................................................31

SHORT TERM ACTIVITIES.......................................................................................31LONG TERM ACTIVITIES.........................................................................................34

III-G TsunamiPage of 34

Part III-G – Tsunami

A. CALIFORNIA TSUNAMI THREATA tsunami is a wave triggered by any form of land displacement along the edge or bottom of an ocean or lake. This can be submarine landslides or submarine dip slip fault ruptures that result in seafloor uplift or down-drop. This mass movement translates to a tsunami or gravity wave within the overlying water.

Tsunamis travel outward from the point of initiation. The size of a tsunami is proportional to the mass movement that generated the tsunami. The speed of a tsunami is proportional to the depth of the water in which the tsunami originated. Tsunamis can travel at great speeds but in the open ocean result in relatively little wave height above the mean sea level as the energy is distributed throughout the water column. The wave length of a tsunami is much longer than wind generated waves, making it hard to detect in the open ocean.

As a tsunami approaches the shore and the depth of the water column decreases, the energy in the wave pushes the wave crest above the water surface resulting in a large wave height. Wave run-up is the elevation above mean sea level on dry land that a tsunami reaches. Run-up is what causes inundation of coastal areas that are below the run-up height. Identifying tsunami hazards requires 1) evaluating the potential for submarine mass movement both locally and at great ocean distances, and 2) identifying coastal regions within the direct or indirect path of a potential tsunami wave that are below the run-up height.

There are two types of tsunamis, local and distance. Local tsunamis are more threatening because they afford at-risk populations only a few minutes to find safety. California is vulnerable to, and must consider, both types.

Tsunamis can travel at speeds of over 600 miles per hour in the open ocean and can grow to over 50 feet in height when they approach a shallow shoreline, causing severe damage to coastal development. In 1997, a large tsunami triggered by a Magnitude 7 earthquake killed more than 3, 500 people in Papua, New Guinea. The 1964 Alaskan Earthquake produced a tsunami that killed 13 people and caused over $10 million in damage in Northern California; damage and losses were even greater in Hawaii.

The March 2011 earthquake in Japan caused a giant tsunami that devastated Japan. Most of the damage was caused by the tsunami which caused fires, a dam failure, destroyed hundreds of structures, displaced tens of thousands of residents and damaged nuclear power plants to the point of causing partial meltdowns in several of the reactors.

Recent studies of the continental shelf off the California coast indicate a potential for underwater landslides capable of generating damaging tsunamis that could threaten coastal communities including Newport Beach where the Coast Community College District (CCCD) Sailing Center is located on the beach.

CAUSES OF A TSUNAMI


There are many causes of tsunamis, but the most prevalent is earthquakes. In addition, landslides, volcanic eruptions, explosions, and even the impact of cosmic bodies, such as meteorites, can generate tsunamis.

PROFILING TSUNAMI HAZARDS

Recent studies have documented historical tsunamis that have been recorded along coastal California. The California Seismic Safety Commission report, the Tsunami Threat to California Findings and Recommendations on Tsunami Hazards Risks, published in December 2005, indicates that over 80 tsunamis have been observed or recorded along the coast of California in the past 150 years. The report includes findings that tsunamis generated either locally or from events elsewhere in the Pacific Basin pose a significant threat to life and property in California, and that tsunamis present a substantial risk to the economy of the state and nation primarily through the impact on ports.

The recently approved 2010 version of the Marine Oil Terminal Engineering and Maintenance Standards, codified as the 2010 California Code of Regulations Title 24, Part 2, California Building Code, Chapter 31F Marine Oil Terminals, will become effective in 2011. It includes a study by Jose Borrero (2006) that provides maximum credible tsunami water levels and current speeds for marine oil terminals in the San Francisco Bay Area. The work by Mark Legg (2002) provides estimated wave height for coastal cities in Southern California. The portion of Northern California north of Mendocino triple junction (roughly offshore due west of the town of Petrolia) falls within the Cascadia seduction zone, which has wave heights by the state mapping agencies.

The National Geodetic Data Center provides a database cataloging all tsunami occurrences. The database can be used to evaluate past tsunami events at a particular site.

ASSESSMENT OF CALIFORNIA VULNERABILITY AND POTENTIAL LOSSES

Assessing vulnerability and potential loss due to tsunami hazards is a field that is in its infancy. Spurred by the catastrophic tsunami in Sumatra (Iwan, 2006), a recent spate of research has been initiated to evaluate relative loss as a function of the built environment and tsunami loading. At this point, there is little in the way of quantitative methods for analyzing vulnerability and loss. Some of the issues that are relatively unknown include structural response to tsunami wave loading, tsunami wave loading forces for design purposes, non-structural element response to wave loading, and dynamic effects of tsunami wave travel throughout a built environment.

Assessment of run-up heights is currently performed by tsunami modelers who have made significant improvements in their ability to properly model wave propagation with respect to complex sea floor topography and 3-D wave mechanics. To have probabilistic run-up heights, the triggering mechanism needs to be related to recurrence intervals such as with flood frequency or earthquake recurrence with respect to complex sea floor topography and 3-D wave mechanics. To have probabilistic run-up heights, the triggering mechanism needs to be related to recurrence intervals such as with flood frequency or earthquake recurrence. The California Geological Survey and Cal EMA are in the initial stages of producing maps that will utilize a probabilistic tsunami hazard analysis for California. These maps will identify potential tsunami


hazard “zones of required investigation” under the Seismic Hazards Mapping Act and will assist state and local agencies in making land use planning decisions.

CURRENT TSUNAMI HAZARD MITIGATION EFFORTS IN CALIFORNIA

A report issued by the California Seismic Safety Commission in 2005 states that “tsunamis, generated either locally or from events elsewhere in the Pacific Basin, pose a significant threat to life and property in California,” and points out that losses from tsunamis can be reduced in four ways:

1. Engineering standards creating more damage-resistant buildings and port structures2. Public education training Californians to recognize tsunami alerts and providing

instruction on what to do3. Warning systems alerting a population to a tsunami coming from a distant source4. Effective evacuation planning

The report recommends a series of actions to be taken to improve mitigation, preparedness, response and recovery including:

Improving public education about tsunami issues, including multi-lingual information Working with other coastal states to obtain an external expert review of the National

Oceanic and Atmospheric Administration (NOAA) tsunami warning system criteria for issuing and canceling warnings

Working with federal agencies to develop guidelines for structures to resist both strong ground motion and tsunami wave impact

Supporting and providing matching funds for tsunami mitigation programs in coastal counties, including improvements to the communications and emergency response systems

Regions that are below the projected run-up height are delineated, and evacuation plans are essentially the only mitigation methods currently available. These have been implemented along the Cascadia subduction zone throughout Washington and Oregon, but most regions of coastal California have yet to adopt these preparations.


Figure 1 - Tsunami Inundation Map, 2009


COASTAL FLOODING, EROSION AND SEA LEVEL RISE

IDENTIFYING COASTAL FLOODING, EROSION AND SEA LEVEL RISE HAZARDS

As discussed earlier, the potential impacts of global warming and climate change include increased opportunities for severe weather and winter storms that may result in coastal flooding and erosion, as well as sea level rise. California’s land mass includes more than 1,100 miles of coastline with varying geologic features including steep coastal bluffs, beaches, wetlands, bays and deltas. It also supports varying levels of development and land use, including recreational, agricultural, industrial, commercial and residential.

PROFILING COASTAL FLOODING, EROSION AND SEA LEVEL RISE HAZARDS

Coastal erosion is a natural geomorphic process. In California, coastal erosion can be accelerated or exacerbated to the level of emergency or disaster through a combination of factors, including winter storms, tidal action, wind-generated high surf, wave action, tsunamis and rising sea levels. Typically, the highest sea level readings along California’s coastline occur during periods of heavy rain that coincide with high tides, causing coastal flooding, coastal bluff erosion, and landslides such as were experienced during the 1998 El Nino storms. Conversely gradual sea level rise progressively worsens the impact of high tides and wind-driven waves associated with severe storms. The frequency of high sea level extremes may be further increased if storms become more frequent or severe as a result of climate change. These events could expose the coast to severe flooding and erosion damage to coastal structures and real estate, and salinity intrusion into delta areas and coastal aquifers.

The continued rise in sea level will increase inundation of low coastal areas especially in tsunamis. The rise in sea level increases the threat to tsunami and in turn would increase the number of individuals living in the threat zone and the economic impact.

The rise in sea level will increase the near-shore wave heights and wave energy will increase intensifying the potential for storm damage, beach erosion and bluff retreat. Ports and harbors will have reduced cargo transfer capability as ships ride higher along the dock. Wetlands may be inundated if they are not able to migrate either vertically or landward. Almost all coastal systems will be affected; even groundwater aquifers will be at greater risk from saltwater intrusion, a fear in the northwest Orange County coastline.

ASSESSMENT OF STATE AND LOCAL VULNERABILITY AND POTENTIAL LOSS

An early report prepared by the California Coastal Commission staff in June 2001 identified a number of potential consequences from climate change-induced sea level rise, including impacts on ports and harbors, seawalls and other engineered structures, groundwater, wetlands, beaches and coastal bluffs. In assessing overall economic impacts, the Coastal Commission projected areas of the coast where a long-term rise in sea level would be most severe and areas that would experience the greatest economic losses. The projections were based on estimates of coastal population growth to over 32 million by 2025 with an anticipated


20 to 60 percent increase in coastal economic growth, except for San Diego, which is anticipated to experience a 60 to 90 percent growth.

More recently, a range of future sea level rise scenarios have been estimated but they may not adequately capture all the contributions from ice sheet melt and other dynamics. The current thinking of the California Climate Action Team, a cabinet-level policy group under the Governor, projects that sea level rising will range from 20 to 55 inches (0.5 to 1.4 meters) by 2100. This estimate surpasses the team’s 2006 estimate of 12 to 36 inches, which was used in the 2007 State Hazard Mitigation Plan. The Pacific Institute concludes that under medium to medium-high greenhouse gas emissions scenarios mean sea level rise will range from 1.0 to 1.4 meters. Considerable critical infrastructure will be impacted by these rises including 140 schools in California.

The threat of a tsunami along with the rising sea level compounds the problem. These issues together should be considered in CCCD future land use planning and current mitigation planning.

EARTHQUAKES AND TSUNAMIS

An earthquake can be caused by volcanic activity, but most are generated by movements along fault zones associated with plate boundaries. Most strong earthquakes, representing 80% of the total energy released worldwide by earthquakes, occur in subduction zones where an oceanic plate slides under a continental plate or another younger oceanic plate.

Not all earthquakes generate tsunamis. To generate a tsunami, the fault where the earthquake occurs must be underneath or near the ocean, and cause vertical movement of the sea floor over a large area, hundreds or thousands of square miles. By far, the most destructive tsunamis are generated from large, shallow earthquakes with an epicenter or fault line near or on the ocean floor. The amount of vertical and horizontal motion of the sea floor, the area over which it occurs, the simultaneous occurrence of slumping of underwater sediments due to the shaking, and the efficiency with which energy is transferred from the earth’s crust to the ocean water are all part of the tsunami generation mechanism. The sudden vertical displacements over such large areas disturb the ocean's surface, displace water, and generate destructive tsunami waves. Although all oceanic regions of the world can experience tsunamis, the most destructive and repeated occurrences of tsunamis are in the Pacific Rim region.

TSUNAMI EARTHQUAKESThe September 2, 1992 earthquake (magnitude 7.2) was barely felt by residents along the coast of Nicaragua. Located well off-shore, the severity of shaking on a scale of I to XII, was mostly II along the coast, and reached III at only a few places. 20 to 70 minutes after the earthquake occurred, a tsunami struck the coast of Nicaragua with wave amplitudes up to 13 feet above normal sea level in most places and a maximum run-up height of 35 feet. The waves caught coastal residents by complete surprise; causing many casualties and considerable property damage.


This tsunami was caused by a tsunami earthquake, an earthquake that produces an unusually large tsunami relative to the earthquake magnitude. Tsunami earthquakes are characterized by a very shallow focus, fault dislocations greater than several meters, and fault surfaces that are smaller than for a normal earthquake.

Tsunami earthquakes are also slow earthquakes, with slippage along the fault beneath the sea floor occurring more slowly than it would in a normal earthquake. The only known method to quickly recognize a tsunami earthquake is to estimate a parameter called the seismic moment using very long period seismic waves (more than 50 seconds/cycle). Two other destructive and deadly tsunamis from tsunami earthquakes have occurred in recent years in Java, Indonesia (June 2, 1994) and Peru (February 21, 1996).

Less frequently, tsunami waves can be generated from displacements of water resulting from rock falls, icefalls and sudden submarine landslides or slumps. Such events may be caused impulsively from the instability and sudden failure of submarine slopes, which are sometimes triggered by the ground motions of a strong earthquake. For example, in the 1980's, earth moving and construction work of an airport runway along the coast of Southern France, triggered an underwater landslide, which generated destructive tsunami waves in the harbor of Thebes.

TSUNAMI CHARACTERISTICS

SPEEDUnnoticed tsunami waves can travel at the speed of a commercial jet plane, over 500 miles per hour. They can move from one side of the Pacific Ocean to the other in less than a day. This great speed makes it important to be aware of the tsunami as soon as it is generated. Scientists can predict when a tsunami will arrive at various places by knowing the source characteristics of the earthquake that generated the tsunami and the characteristics of the sea floor along the paths to those places. Tsunamis travel much slower in more shallow coastal waters where their wave heights begin to increase dramatically.

SIZEOffshore and coastal features can determine the size and impact of tsunami waves. Reefs, bays, entrances to rivers, undersea features and the slope of the beach all help to modify the tsunami as it attacks the coastline. No one knows how the Santa River and its adjoining channels will be impacted by a tsunami. When the tsunami reaches the coast and moves inland, the water level can rise many feet. In extreme cases, water level has risen to more than 50 feet for tsunamis of distant origin and over 100 feet for tsunami waves generated near the earthquake’s epicenter. The first wave may not be the largest in the series of waves. One coastal community may see no damaging wave activity while in another nearby community destructive waves can be large and violent. The flooding can extend inland by 1000 feet or more, covering large expanses of land with water and debris.

FREQUENCYSince scientists cannot predict when earthquakes will occur, they cannot determine exactly when a tsunami will be generated. However, by looking at past historical tsunamis and run-up maps, scientists know where tsunamis are most likely to be generated. Past tsunami height


measurements are useful in predicting future tsunami impact and flooding limits at specific coastal locations and communities.

TYPES OF TSUNAMIS

PACIFIC-WIDE AND REGIONAL TSUNAMISTsunamis can be categorized as Pacific-wide and “local.” Typically, a Pacific-wide tsunami is generated by major vertical ocean bottom movement in offshore deep trenches. A ”local” tsunami can be a component of the Pacific-wide tsunami in the area of the earthquake or a wave that is confined to the area of generation within a bay or harbor and caused by movement of the bay itself or landslides.

The last large tsunami that caused widespread death and destruction throughout the Pacific was generated by an earthquake located off the coast of Chile in 1960. It caused loss of life and property damage not only along the Chile coast but also in Hawaii and as far away as Japan. The Great Alaskan Earthquake of 1964 killed 106 people and produced deadly tsunami waves in Alaska, Oregon and California.

There have been smaller tsunamis since then that have caused lesser damage. On April 18, 2011 President Obama declared a major disaster for California in response to tsunami damage from Japan’s major earthquake and tsunami. The majority of the damage occurred along the Santa Cruz and Del Norte coastal areas. The tsunami that devastated parts of Japan serves as a reminder of California's vulnerability to these types of disasters.

July 1993, a tsunami generated in the Sea of Japan killed over 120 people in Japan. Damage also occurred in Korea and Russia but spared other countries since the tsunami wave energy was confined within the Sea of Japan. The 1993 Japan Sea tsunami is known as a “regional event” since its impact was confined to a relatively small area. For people living along the northwestern coast of Japan, the tsunami waves followed the earthquake within a few minutes.

During the 1990's, destructive regional tsunamis also occurred in Nicaragua, Indonesia, the Philippines, Papua New Guinea, and Peru, killing thousands of people. Others caused property damage in Chile and Mexico. Some damage also occurred in the far field in the Marquesas Islands (French Polynesia) from the July 30, 1995, Chilean and February 21, 1996, Peruvian tsunamis.

In less than a day, tsunamis can travel from one side of the Pacific to the other. However, people living near areas where large earthquakes occur may find that the tsunami waves will reach their shores within minutes of the earthquake. For these reasons, the tsunami threat to many areas such as Alaska, the Philippines, Japan and the United States West Coast can be immediate (for tsunamis from nearby earthquakes which take only a few minutes to reach coastal areas) or less urgent (for tsunamis from distant earthquakes which take from three to 22 hours to reach coastal areas).


All of the coastal areas in Orange County are susceptible to tsunamis. A tsunami from the south pacific or from South America could strike the County coastal areas from the south to southwest. The Channel Islands do not provide adequate protection.

The worst recorded tsunami to hit California was in 1812. A landslide occurred in the Santa Barbara Channel, and the resulting waves are reported by some disputed sources to have been up to 15 feet above sea level in Ventura. Again, wide spread damage and some loss of life occurred in 1964 following the Alaskan earthquake. Tsunamis from the earthquake also destroyed a number of towns in Alaska and damaged the Los Angeles-Long Beach harbors, as well as harbors in Ventura County.

In that 1964 Alaska 8.2 Earthquake, tidal surges of approximately 4 to 5 feet hit the Huntington Harbour area in Huntington Beach causing moderate damage.

Personal InterviewName: Bill RichardsonTitle: Huntington Beach LifeguardYear: 1964 – Alaska Good Friday Earthquake and Tsunami(Paraphrased by Glorria Morrison, City of Huntington Beach Emergency Services Coordinator, 2004)

I was the lifeguard working in the tower on the pier. We received warning by phone from the Fire Department who had received information from the National Weather Service. We were told to tell folks on the pier and beach that if the situation escalated they would be advised to evacuate the area and that they should be prepared to move quickly.

I witnessed heavy title surges on the beaches. The tide changed in 10 minutes from what it normally was to a very different tide. Normally it takes six hours to change and in 10 minutes it sucked water out and when it came in, it went over the berm, three quarters of the way up the beach. The accelerated tide came within one hour and it did this twice. The highs were extreme and the lows were extreme, very like our astronomical tides. I monitored the radio and heard of all the docks breaking loose in the harbor. The current was so strong and movement of water that the radio was being overwhelmed with calls for response. Today Huntington Harbour is made up of five islands. Only the two of the islands existed at the time, Admiralty and Gilbert.

Bill Richardson referred me to Walt Sawyer a Lifeguard Lieutenant at the time. Walt was assigned to Huntington Harbour during for this event.

Personal InterviewName: Walt SawyerTitle: Huntington Beach City Lifeguard Lieutenant (assigned to Huntington

Harbour the day of the tsunami)Year: 1964 – Alaska Good Friday Earthquake and Tsunami(Paraphrased by Glorria Morrison, City of Huntington Beach Emergency Services Coordinator, 2004)


I was called out at daybreak due to the tidal surges in the Huntington Harbour. I got in the City’s only rescue boat. The tidal surges were huge and making whirlpools. They were moving at a much faster and higher rate than normal tide.

When the surges would come in, they would tear the boats away from their moorings. Then when the surges would go out, they would take the boats through the bridge at Pacific Coast Highway to the Seal Beach (Anaheim Landing Bridge) and when they hit the pilings it would tear the boats apart. The high tides were carrying the boats into the Seal Beach Weapons Station. When surges retreated the boats would end up on dry land at the weapons station high and dry and broken up.

In 1964, there were only about 200-300 boats in the harbor and today, Walt estimated there are 3,500 plus boats. There were only 300-400 homes then and now he estimates an excess of 5,000. This occurred during a low tide. The sea wall in Huntington Harbour is 9 feet. Had this occurred during a high tide, Walt stated he estimates the surges would have easily gone over the sea walls and damaged many homes.

The historic record indicates that there is a small probability of occurrence of a major tsunami in Orange County. Statistically, it has been over 170 years since the last major tsunami. The immediate or primary effects of a tsunami are easily visualized but the secondary effects can be unanticipated. Water systems can be contaminated, power disrupted, transportation systems blocked or dislocated, increased occurrence of fires from broken oil and gas tanks or lines, flooding from blocked rivers, and possible damage to personal property along coastal areas.

TSUNAMI AS A THREAT TO SOUTHERN CALIFORNIA

History has shown that the probability of a tsunami in Orange County is an extremely low threat. However, if a tsunami should occur, the consequences would be great. That is why we must plan for and mitigate a tsunami event. The entire 43 miles of Orange County coastline could be impacted. Approximately 89,000 residents would have to be evacuated. The impact could cause loss of life, destroy thousands of high priced homes and greatly affect coastal businesses and impact tourism and the economy. Even if all residents and visitors were safely evacuated, the damage to property in this densely populated, high property value area would still be tremendous.

HISTORY OF REGIONAL TSUNAMIS

LOCALThe local tsunami may be the most serious threat as it strikes suddenly, sometimes before the earthquake shaking stops. Alaska has had six serious local tsunamis in the last 80 years and Japan has had many more including the March 2011 devastating earthquake and tsunami.

HISTORY OF LOCAL TSUNAMISTsunamis have been reported since ancient times. They have been documented extensively in California since 1806. Although the majority of tsunamis have occurred in Northern California,


Southern California has been impacted as well. In the 1930’s, four tsunamis struck the Los Angeles, Orange County, and San Diego coastal areas. In Orange County the tsunami wave reached heights of 20 feet or more above sea level. In 1964, following the Alaska 8.2 earthquake, tidal surges of approximately 4 feet to 5 feet hit Orange County’s Huntington Harbour area causing moderate damage.

The run-up is the height the tsunami reached above a reference level such as mean sea level. It is not always clear which reference level was used.

Figure 2 - Maximum Run up -- Water Height above Sea Level in meters.

TSUNAMI HAZARD ASSESSMENT

HAZARD IDENTIFICATIONA tsunami threat to Orange County is considered low to moderate.

DAMAGE FACTORS OF TSUNAMISTsunamis cause damage in three ways: inundation, wave impact on structures, and erosion. Orange County has southwestern facing beaches that are vulnerable to tsunamis or tidal surges from the south and from the west.

Strong, tsunami-induced currents lead to the erosion of foundations and the collapse of bridges and sea walls. Flotation and drag forces move houses and overturn railroad cars. Considerable damage is caused by the resultant floating debris, including boats and cars that become dangerous projectiles that may crash into buildings, break power lines, and may start fires. Fires from damaged ships in ports or from ruptured coastal oil storage tanks and refinery facilities can cause damage greater than that inflicted directly by the tsunami. Of increasing concern is the potential effect of tsunami draw down, when receding waters uncover cooling


water intakes of nuclear power plants. We have all witnessed the devastation a tsunami can have on even well built power plants as the result of the March 2011 Japan earthquake.

Predicted wave heights, exclusive of tide and storm generated wave heights are approximately (Huntington Beach statistics used):

For a 100 year occurrence for a 500 year occurrence4.0 feet minimum 6.8 feet minimum6.6 feet average 11.4 feet average9.2 feet maximum 16.0 feet maximum


Figure 3 - Tsunami Run Up Map for Orange County


TSUNAMI WATCHES AND WARNINGS

WARNING SYSTEMThe tsunami warning system in the United States is a function of the National Oceanic and Atmospheric Administration’s (NOAA) National Weather Service. Development of the tsunami warning system was impelled by the disastrous waves generated in Alaska in April 1946, which surprised Hawaii and the U.S. West Coast, taking a heavy toll in life and property.

The disastrous 1964 tsunami resulted in the development of a regional warning system in Alaska. The Alaska and West Coast Tsunami Warning Center is in Palmer, Alaska. This facility is the nerve center for an elaborate telemetry network of remote seismic stations in Alaska, Washington, California, Colorado, and other locations. Tidal data is also telemetered directly to the ATWC from eight Alaskan locations. Tidal data from Canada, Washington, Oregon, and California are available via telephone, teletype, and computer readout.

WATCH VS. WARNINGThe National Warning System (NAWAS) is an integral part of the Alaska Tsunami Warning Center. Reports of major earthquakes occurring anywhere in the Pacific Basin that may generate seismic sea waves are transmitted to the Honolulu Observatory for evaluation. An Alaska Tsunami Warning Center is also in place for public notification of earthquakes in the Pacific Basin near Alaska, Canada, and Northern California. The Observatory Staff determines action to be taken and relays warnings over the NAWAS circuits to inform and warn West Coast states. The State NAWAS circuit is used to relay the information to the Orange County Operational Area, which will in turn relay the information to local warning points in coastal areas. The warning points for Orange County cities are the Police Departments. In Orange County, the Sheriff Department as well as local Police Departments are responsible for warning the public of a tsunami and for conducting evacuations away from coastal areas. The same information is also transmitted to local jurisdictions over appropriate radio systems, teletype, email, and telephone circuits to ensure maximum dissemination.

The Local Warning Point for Orange County is the OCSD Watch Commander’s Office. The 24-hour a day on-duty Watch Commanders are responsible for activating appropriate county agencies and personnel and the emergency management staff for the County’s Emergency Operations Center (EOC) if needed. A Tsunami Watch Bulletin is issued if an earthquake has occurred in the Pacific Basin and could cause a tsunami. A Tsunami Warning Bulletin is issued when an earthquake has occurred and a tsunami is spreading across the Pacific Ocean. When a threat no longer exists, a Cancellation Bulletin is issued. Also, an Advisory Bulletin may be issued to provide information to local communities and the public.

EVACUATIONUpon receipt of a Tsunami Watch/Warning Bulletin, an immediate (voluntary or mandatory) evacuation may be ordered depending on the potential threat to the coastal areas of Orange County. After a thorough evaluation, a determination will be made as to the degree of evacuation necessary to eliminate any threats to the resident and visiting populations.

Once the degree of evacuation has been determined, officers will block all movements on Pacific Coast Highway except those necessary to gain access to the nearest arterial highway leading away from the ocean. The population will be directed inland using the closest available northbound or eastbound arterial highway. It is imperative that the evacuation routes be kept


open and clear at all times. When the CCCD receives a Tsunami Warning or Advisory Bulletin, they should immediately notify the Orange Coast Sailing Center of the incident.

Additionally, if a large tsunami were to hit the Orange County coastline, approximately 89,000 local residents would have to be evacuated to neighboring cities such as Costa Mesa, Westminster or other inland cities. Neighboring jurisdictions along with the American Red Cross would be called upon for care and shelter duties. Displacing residents, utilization of District, City and County resources and disaster cleanup can cause an economic hardship on all impacted communities. The CCCD should be prepared to shelter any students, employees and the community left homeless by the evacuation or for longer-term shelters should the tsunami damage homes along the coast.

VULNERABILITY AND RISKWith an analysis of tsunami events depicted in the “Local History” section, we can deduce the common tsunami impact areas will include impacts on life, property, infrastructure (including CCCD) and transportation.

COMMUNITY TSUNAMI ISSUES

SUSCEPTIBILITY TO TSUNAMI

Life and PropertyBased on the “local” history events of tsunamis we can conclude that a small percent of the County would be heavily impacted utilizing the Tsunami Run-up Maps. The largest impact on the community from a tsunami event is the loss of life and property.

Known risk areas include, but are not limited to:

City, County and State Beaches All buildings and apartments on the water side of Pacific Coast Highway (PCH) Vehicles and pedestrians on PCH in low lying areas Buildings that are on the inland side of PCH facing the ocean Harbor areas Low lying areas adjacent to the coast

In a Pacific-wide tsunami, the Tsunami Warning and Watch Bulletin would provide time to allow coastal residents to evacuate and seek higher ground for shelter. This would greatly reduce injuries and loss of life.

ResidentialAlso property along the coast could be devastated. Orange County is an affluent community; the median price of a home on the coastline is $800,000 to $1 million+ dollars. A large tsunami could potentially destroy or damage hundreds of homes spreading debris for miles. A tsunami would severely impact northwest coastal Orange County.

Commercial


The coastline of Orange County is world famous. During summer months hundreds of thousands of people a day come into the community to stay in the beautiful hotels and shop at the unique boutiques. Local governments rely heavily on tourism and sales tax. A tsunami event would impact businesses by damaging property and by interrupting business and services. Any residential or commercial structure with weak reinforcement would be susceptible to damage.

InfrastructureTsunamis (and earthquakes) can damage buildings, power lines, and other property and infrastructure due to flooding. Tsunamis can result in collapsed or damaged buildings or blocked roads and bridges, damaged traffic signals, streetlights, and parks, among others. Damage to public water and sewer systems, transportation networks, and flood channels would greatly impact daily life for residents.

Roads blocked by objects during a tsunami may have severe consequences to people who are attempting to evacuate or who need emergency services. Emergency response operations can be complicated when roads are blocked or when power supplies are interrupted. Industry and commerce can suffer losses from interruptions in electric services and from extended road closures. They can also sustain direct losses to buildings, personnel, and other vital equipment. There are direct consequences to the local economy resulting from tsunamis related to both physical damages and interrupted services.

Existing Mitigation ActivitiesOrange County has implemented a number of tsunami mitigation activities over the years. Some of the current mitigation programs include:

Public Information Plan for Emergency Alerting System (EAS) Disaster Preparedness Public Education for Tsunami Preparedness NOAA’s TsunamiReady Program certification

Orange County California was the first county in the U.S. to have every coastal city and the county certified as TsunamiReady by NOAA. Following the Sumatra tsunami of December 24, 2004, the County, its Cities, Special Districts and School Districts concentrated their efforts on getting prepared for tsunamis, conducting public educations and held tsunami exercises. CCCD participated in the 2005 Orange County Operational Area Tsunami Exercise. They joined the City of Huntington Beach, City of Costa Mesa, City of Westminster, City of Fountain Valley, Huntington Beach City School District, Huntington Beach Unified High School District, Ocean View School District, State Beach and California Office of Emergency Services (now Cal EMA) in a joint exercise in Huntington Beach. The exercise was both educational for all participants and gave everyone the opportunity to work together in preparing for and responding to a tsunami.


B. HAZUS

HAZUS is a regional multi-hazard loss estimation model that was developed by the FEMA and the National Institute of Building Sciences. The primary purpose of HAZUS is to provide methodology and software application to develop multi-hazard losses at a regional scale. These loss estimates would be used primarily by local, state and regional officials to plan and simulate efforts to reduce risks and to prepare for emergency response and recovery. It cannot be emphasized enough that the HAZUS loss estimates are exactly that, estimates. The study discussed in this plan was the Orange County HAZUS Study dated April 23, 2009.

Table 1 - Orange County General Building Stock

Essential Facility Inventory


For essential facilities, there are 157 hospitals in the region with a total bed capacity of 6,317 beds. There are 5,733 schools, 139 fire stations, 67 police stations and 38 emergency operation centers.

Table 2 - Orange County General Building Stock Damage


DEBRIS GENERATION

HAZUS estimates the amount of debris that will be generated by the tsunami flooding. The model breaks debris into three general categories:

Finishes (dry wall, insulation, etc.) Structural (wood, brick, etc.) Foundations (concrete slab, concrete block, rebar, etc.)

This distinction is made because of the different types of material handling equipment required to handle the debris.

The model estimates that a total of 948,070 tons of debris will be generated. Of the total amount

Finishes comprises 38% of the total Structures comprises 32% of the total

If the debris tonnage is converted into an estimated number of truckloads, it will require 37,923 truckloads (@25 tons/truck) to remove the debris generated.

SHELTER REQUIREMENTS

HAZUS estimates the number of households that are expected to be displaced from their homes due to the flood and the associated potential evacuation. HAZUS also estimates those displaced people that will require accommodations in temporary public shelters. The model estimates 23,157 households will be displaced due to the damage. Displacement includes households evacuated from within or very near to the inundated area. Of these, 64,002 people (out of a total population of 2,926,756) will seek temporary shelter in public shelters.

The CCCD should be prepared to shelter any students and employees who live along the coast and may not be able to return home in a tsunami warning. Also, the CCCD has signed an agreement with the American Red Cross (as did all public schools in Orange County) to operate as a public shelter. 23,157 households may be left homeless should the tsunami cause destruction along the Orange County coast. The CCCD facilities would be needed as public shelters.

ECONOMIC LOSS

The total economic loss estimated for the tsunami flood is 2,783.84 million dollars, which represents 30.5% of the total replacement value of the scenario buildings.


Building-Related LossesThe building losses are broken into two categories:

Direct building losses Business interruption losses

The direct building losses are the estimated costs to repair or replace the damage caused to the building and its contents. The business interruption losses are the losses associated with inability to operate a business because of the damage sustained during the flooding. Business interruption losses also include the temporary living expenses for those people displaced from their homes because of the incident.

The total building-related losses were $2.8 billion dollars. One percent of the estimated losses were related to the business interruption of the region. The residential occupancies made up 74.19% of the total loss. The table below provides a summary of the losses associated with the building damage.

Table 3 - Building-Related Economic Loss Estimates

Table 4 - Summary of Impacts on OC for Tsunami

Impact Category TsunamiEconomic Loss due to Building DamageTotal Building-related Direct Economic Loss

$2.8 B$2.8 B

# Buildings in Complete Damage State 1,928Debris Generated (million tons) 0.95Displaced HouseholdsPeople Needing Short-term Shelter

23,157 Households64,002 People

# Highway Bridges w/ at least Moderate Damage (potentially closed)

0


Table 5 - Summary of Impacts Orange County Essential Facilities

Essential Facility Category

Hospital

SmallMediumLarge

Schools

K-12 (default data)K-12 (providing data)CCD (providing data)

EOCsPolice StationsFire StationsTOTALS

Table 6 - Orange County School Districts - ASCIP provided Site-Specific Data

District Type District NameK-12 School Districts Brea Olinda Unified School District

Capistrano Unified School DistrictFullerton Joint Union High School DistrictFullerton School DistrictHuntington Beach City School DistrictHuntington Beach Union High School DistrictLaguna Beach Unified School DistrictNewport-Mesa Unified School DistrictOcean View School DistrictOrange County Dept. Of EducationPlacentia-Yorba Linda Unified School DistrictSanta Ana Unified School DistrictTustin Unified School District

Community College Districts North Orange County Community College DistrictRancho Santiago Community College District


TSUNAMI COASTAL FLOOD

In addition to three river flooding scenarios, Orange County was subjected to a hypothetical tsunami. With its location along the Pacific Ocean’s “ring of fire” and having highly developed coastal communities, a tsunami flood scenario in the county is possible (although rare) and could create significant building losses. The flood hazard area for the tsunami event was derived from a county tsunami inundation map created by the University of Southern California Tsunami Research Center under the guidance of the California Emergency Management Agency (Cal EMA). A suite of tsunami source events (18 events – 6 local sources and 12 distant historical sources) were modeled using the Method of Splitting Tsunamis (MOST) computational program to define an inundation line along the Orange County coastline representing the maximum considered tsunami run-up. The Orange County “Tsunami Inundation Map for Emergency Planning” is available from Cal EMA.

As shown below, the most extensive flooding occurs in the northwestern coastal portion of the county, in the areas of Seal Beach, Huntington Beach, Costa Mesa and Newport Beach. The Dana Point area also experiences extensive flooding. Flood depths in these areas may run as high as 129 feet deep. Flooding may occur as much as 9,450 feet inland from the coast.

Figure 4 - Orange County Tsunami Inundation Areas


REGIONAL IMPACTS

The tsunami flood scenario will primarily impact the northwestern coastal communities (Huntington Beach, Newport Beach, Balboa Island and Lido Island) and infrastructure of Orange County. A summary of regional tsunami impacts is provided in the table below. The impacts are described below and are tabulated in greater detail in the HAZUS Global Summary Report for this scenario tsunami.

Table 7 - Summary of Impacts for Orange County due to a Tsunami

Impact Category HAZUS Estimated ImpactEconomic Loss due to Building DamageTotal Building-related Direct Economic Loss

$2.76 B$2.77 B

# Buildings in Complete Damage State 1,928 Debris Generated (million tons) 0.95 Displaced HouseholdsPeople Needing Short-term Shelter

23,157 Households64,002 People

# Highway Bridges w/ at least Moderate Damage (potentially closed)

0

In an Orange County tsunami, direct economic losses due to building damage are estimated to reach $2.76 billion and total building direct economic losses are expected to reach $2.77 billion. The geographic distribution of total direct economic loss is mapped below.

Figure 5 – OC Total Direct Economic Loss resulting from Tsunami Flood Scenario


Of the approximately 738,000 buildings modeled within the general building stock for Orange County, much less than 1% (1,928) are expected to suffer “Complete” damage in the 1% annual chance flood event (100-year flood) scenario. These building would be considered “red-tagged” or unsafe for continued occupancy. Just over half (54%) of the 1,928 buildings are wood construction and about 43% are manufactured housing (i.e., mobile homes). Approximately 11,000 buildings (1.5%) are expected to suffer more than 20% damage or more while about 1,900 buildings are estimated to suffer flood damage of less than 20%. As much as 0.95 million tons of debris may result from these damaged buildings – 30% is expected to be heavy debris (concrete and steel), requiring heavy equipment to break down and remove, while 70% is expected to be light debris (wood, brick, drywall and other debris).

Damage to single family and multi-family dwellings is expected to result in the displacement of almost 23,000 households. While many of the displaced may find shelter with friends and family, or in available hotels, as many as 64,000 people are expected to seek short-term public shelter. While not as large a displaced population and short-term sheltering need as the other flood scenarios, this large number of people could still tax the emergency sheltering capacity of the county. Displaced populace should be able to move to safe locations without too much difficulty. All the bridges servicing the coastal areas of the county are expected to remain functional.

ESSENTIAL FACILITY IMPACTS

Table 4-37 provides an overview of essential facility performance in the tsunami flood scenario. The table lists the number of essential facility sites and buildings (these numbers will differ for multi-building campuses, such as schools and hospitals). The table also provides the total building replacement value, and the number of buildings for which value data was available. As can be seen in the table, replacement cost data for hospitals was generally not available, unlike most other essential facility types. Expected building damage in this flooding event for all essential facility types is 0%. No economic losses are estimated for essential facilities, showing that all essential facilities are located far enough away from the shore to avoid being impacted by the tsunami event considered.


Table 8 - Orange County Essential Facility Loss Estimates – Tsunami Flood Scenario

Essential Facility

Category

No. ofFacilities/Sites

No. of Buildings

No. of Beds

Replace-ment Cost ($1,000)

# Buildings withReplace-ment cost data

# Non-Functional Buildings

Time to Restore (Days)

Economic Loss ($1,000)

Hospital

Small 2 3 78 $0 0 0 0 $0

Medium 10 33 1,01

8 $50,000 7 0 0 $0

Large 20 121 5,22

1 $677,998 12 0 0 $0

Schools

K-12 (defaultdata) 560 569 $335,710 569 0 0 $0K-12 (providingdata) 346 4,952

$2,983,628 4,840 0 0 $0

CCD (providingdata) 22 212 $461,676 207 0 0 $0

EOCs 38 38 $368,079 38 0 0 $0PoliceStations 67 67 $770,105 67 0 0 $0FireStations 139 139 $316,580 135 0 0 $0

TOTALS 1,204 6,134 6,31

7 $5,963,77

6 5,875 0 0 $0Note: No percentages or cost estimates available for schools

C. CCCD TSUNAMI DAMAGE ESTIMATES

The CCCD has only one property located in the tsunami impact area, the Orange Coast College Sailing Center in Newport Beach, an 11,569 square foot property with a replacement value of $3,751,040.

III-G TsunamiPage 27 of 34

Table 9 - List of CCCD Sites and Vulnerability Rankings for Tsunami

Identifier Site Name Owned or Leased Damaged

(Yes or No)

A1* College District OfficeCosta Mesa Owned No

A2 KOCE TransmitterLa Habra Heights Owned No

A3* Transportation FacilityCosta Mesa, Owned No

B1* Orange Coast CollegeCosta Mesa Owned No

B2 Orange Coast Sailing Center inNewport Beach Owned

Yes

C1* Golden WestCollege, HB Owned No

D1* Coastline Administrative CenterFountain Valley Owned No

D2 Coastline Art GalleryHuntington Beach Owned No

D3 Coastline Costa Mesa CenterCosta Mesa Leased No

D4* Coastline Garden Grove CenterGarden Grove Owned No

D5 Coastline Le-Jao CenterWestminster Owned

No

D6 Coastline Newport Beach CenterNewport Beach Owned No

D7 Coastline OC Regional One Stop-IrvineIrvine Leased No

D8 Coastline OC Regional One Stop Center-WmWestminster Leased No

D9 Coastline Tech CenterFountain Valley Leased No


Table 10 - CCCD Tsunami Damage Estimates by Site

Identifier Site Name Asset

CountTotal

Square Footage

Total Replacemen

t Cost

Orange County

Tsunami

A1 Coast Community College District Office 4 73,892 29,762,830 0

A2 KOCE Transmitter 2 1,749 1,332,000 0A3 Transportation Facility 1 7,712 2,439,200 0B1 Orange Coast College 158 942,869 324,736,020 0

B2 Orange Coast College Sailing Center 2 11,569 3,751,040 Not Available

C1 Golden West College 86 652,890 232,811,780 0

D1Coastline Community College Administrative Center, FV

2 61,505 21,437,100 0

D2 Coastline Community College Art Gallery 1 3,283 131,300 0

D3 Coastline Costa Mesa Center, CM 15 27,577 736,400 0

D4 Coastline Community College GG Center, GG 1 48,000 22,829,000 0

D5 Coastline Community College Le-Jao Center 3 28,067 10,598,900 0

D6 Coastline Community College NB Center, NB 0

D7 Coastline Regional One Stop Center Irvine 1 21,420 646,700 0

D8 Coastline Regional One Stop Center, Wm 1 24,992 693,000 0

D9 Coastline Community College Tech Center, FV 1 0

TOTALS 651,905,270 Not Available

Note: This table will have to be completed in the future when CCCD is included in a new HAZUS study


EARTHQUAKE AND CCCD DEVELOPMENT TRENDS

The only facility in the planning/building process in the CCCD is the future Newport Beach Center. It will be located at 1515 Monrovia Avenue in Newport Beach and completed in June 2012. According to the Newport Beach City Emergency Manager, this site to be built is not located in the tsunami impact zone.

The Project Manager and contractor met with the Newport Beach Emergency Services Coordinator in March 2011 to determine all the hazards that could impact the Newport Beach sites. It helps to understand the threats by contrasting the two Newport Beach sites. As a result of the meeting and the earthquake research, the following information has been learned:

The two Newport Beach sites have entirely different threats for earthquake, flood and tsunami

The Sailing Center in Newport Beach is on Pacific Coast Highway, directly across the street from the Pacific Ocean and has a serious threat of tsunami

The new Newport Beach Center is not coastal, is located up on a hillside and does not have a tsunami threat following earthquake


D. CCCD TSUNAMI MITIGATION STRATEGIES

SHORT TERM ACTIVITIES

Hazard: Tsunami Short Term Activity #1Action Item: Participate in the Orange County HAZUS ProjectCoordinating Organization:

EHS/Emergency Management Coordinator and Vice Chancellor of Administrative Services

Ideas for Implementation:

Research how CCCD can participate in the Orange County HAZUS Project

Provide CCCD building inventory and cost estimates to Orange County HAZUS Project

In 5 years, when the Hazard Mitigation Plan is revised, improve the risk analysis by incorporating CCCD HAZUS data; use revised HAZUS hazard maps and cost estimates in the plan update; use this information to further assist in prioritizing mitigation activities and assessment

Time Line: 5 yearsConstraints: This strategy must be approved by the Orange County Hazard Mitigation

Planning Task Force Plan Goals Addressed

Promote Public AwarenessX Create Partnerships and Implementation

Protect Life and PropertyProtect Natural SystemsStrengthen Emergency Services


Hazard: Tsunami Short Term Activity #2Action Item: Design and install a Tsunami Alerting System in the Orange Coast

College Sailing Center in Newport BeachCoordinating Organization:

EHS/Emergency Management Coordinator and Orange Coast College Emergency Coordinator


Design a Tsunami Alerting System or utilize an existing system for the Orange Coast College Sailing Center

Install system Educate employees on the system

Time Line: 5 yearsConstraints: This strategy must be approved by the Hazard Mitigation Committee and

the CCCD AdministrationPlan Goals AddressedX Promote Public Awareness

Create Partnerships and ImplementationX Protect Life and Property

Protect Natural SystemsX Strengthen Emergency Services

Hazard: Tsunami Short Term Activity #3Action Item: Develop a Tsunami Plan for the Orange Coast College Sailing Center in

Newport BeachCoordinating Organization:



Work with the Orange Coast College Emergency Coordinator to develop a Tsunami Response Plan for the Sailing Center

o Work with the Orange Coast College Emergency Coordinator to develop warning procedures for the Sailing Center

o Work with the Orange Coast College Emergency Coordinator to develop an evacuation plan for the Sailing Center

Determine how the CCCD EOC can assist when a warning is issued and include that information in the CCCD Emergency Operations Plan

Train Sailing Center employees how to carry out the planTime Line: 5 yearsConstraints: This strategy must be approved by the Hazard Mitigation Committee and

the CCCD AdministrationPlan Goals Addressed

Promote Public AwarenessCreate Partnerships and Implementation

X Protect Life and PropertyProtect Natural Systems

X Strengthen Emergency Services


Hazard: Tsunami Short Term Activity #4Action Item: Develop a Tsunami Public Education for the Orange Coast College

Sailing Center in Newport BeachCoordinating Organization:



Develop a Tsunami brochure for the Sailing Center employees and students

Ensure it is included in all class introductions held at the Sailing Center

Add Tsunami Awareness and Preparedness to all CERT/BERT classes




X Protect Life and PropertyProtect Natural Systems

X Strengthen Emergency Services

Hazard: Tsunami Short Term Activity #5

Action Item: Conduct a Tsunami Exercise at the Orange Coast College Sailing Center in Newport Beach for employees

Coordinating Organization:



Develop a Tsunami training and Tabletop Exercise for Sailing Center employees

Conduct the Tsunami Tabletop Exercise Include key CCCD EOC personnel in the exercise


the CCCD AdministrationPlan Goals AddressedX Promote Public Awareness

Create Partnerships and ImplementationX Protect Life and Property

Protect Natural SystemsX Strengthen Emergency Services


LONG TERM ACTIVITIES

Hazard: Tsunami Long Term Activity #1Action Item: Conduct an Orange Coast College Sailing Center facility survey to

determine potential facility mitigation projects Coordinating Organization:

CCCD Facilities Director


Conduct the survey Implement any recommendations as the result of the survey




X Protect Life and PropertyProtect Natural SystemsStrengthen Emergency Services


Part IA - Coast Colleges Home Page TSUNAMI.docx · Web viewPart III-G – Tsunami A.California Tsunami Threat3 Causes of a Tsunami4 Current Tsunami Hazard Mitigation Efforts in California5

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