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A Proposed Seismic Microzonation Study of the City of Santo
Domingo,
Dominican Republic Jay Pulliam1, Victor Hurfano2, Michael
Schmitz3, Carlos Valds-Gonzalez4,
Richie Robertson5, Lyndon Brown6, Eugenio Polanco7
1 Baylor University USA; 2Puerto Rico Seismic Network;
3FUNVISIS, Venezuela; 4UNAM, Mexico City, Mexico; 5Seismic Research
Centre, Trinidad & Tobago; 6Earthquake Unit, UWI
Mona, Jaimaca; 7Instituto Sismologa Universitario, UASD,
Dominican Republic
PLUS! The Puerto Rico Seismic Network:
Earthquake and Tsunami Monitoring
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The mission of the Puerto Rico Seismic Network (PRSN) is to
rapidly determine the location and size of all earthquakes and
tsunamis in the PRSNs Area of Responsibility (AOR) and to
immediately disseminate this information to concerned agencies,
scientists, and the general public. The PRSN compiles and maintains
an extensive seismic database of earthquake parameters, continuous
waveforms (earthquakes, GPS, and sea level) and their effects,
which serves as a foundation for basic and applied earth science
and oceanography research in Puerto Rico and the Caribbean.
PRSN MISSION
The Puerto Rico Seismic Network:
Earthquake and Tsunami Monitoring
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PRSN VIRTUAL NETWORK IU: IRIS/USGS II : IRIS/IDA CU: USGS
Caribbean PR: PRSN/PRSM, Puerto Rico UA: Aruba Meteorological
Agency G : Geoscope GE: Geofone MO: Montserrat Volcano Observatory
NA: KMNI Antilles DR: ISU Dominican Republic, UT UC: Colima
University, Mexico SV: SNET, El Salvador NI: INETER, Nicaragua OV:
OVSICORI, Costa Rica PA: Volcan Baru Network, Panama TR: West
Indies Seismic Research Center CM: Colombian National Seismological
Network CN: Canadian Seismic Network BL : Brazil Seismic Network
MG: National Seismological Service of Mexico CY: Cayman Island
CURRENT REAL TIME EARTHQUAKE MONITORING
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Current real time tsunami monitoring
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PRSN SEISMIC CATALOGUE (AOR)
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PRSN SEISMIC CATALOGUE (AOR)
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ShakeMap in PUERTO RICO
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ShakeMap
Generates maps of the spatial distribution of peak
ground-motions (acceleration, velocity, and spectral response) as
well as a map of instrumentally derived seismic intensities.
These maps provide a rapid visual (and quantitative) estimate of
the extent of potentially damaging shaking during an earthquake and
can be used for emergency response, loss estimation, and for public
information through the media.
The frequency and amplitude dependence of site amplification on
local site geology (average 30-m depth shear velocity) is still a
rapidly evolving area of study.
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Magnitude 7.0 - HAITI REGION Tuesday, January 12, 2010 at
21:53:09 UTC
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WC/ATWC
PTWC
NEIC
ISC
DMC
ASL
IDA
REGIONAL NETWORKS
NOAA
CURRENT REAL TIME DATA SHARING
UNAVCO
COCONet GPS Network
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88 representatives from 22 different countries
14 grad students or postdocs
27 professors
15 people primarily associated with networks or seismology
research
20 others
Among the 20 others are representatives from
World Bank
UNISDR Americas
UNDP
NOAA/NWS
USAID
UNAVCO
IRIS
CTBTO
NSF
Haiti Dominican
Republic Guadeloupe Martinique Jamaica Puerto Rico Trinidad
& Tobago British Virgin
Islands Puerto Rico Venezuela Colombia
Guatemala Costa Rica Honduras Nicaragua Mexico Panama United
Kingdom United States Norway Germany
Sponsored by U.S. National Science Foundation, US Agency for
International Development, American Geophysical Union
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Santo Domingo Population of 3.3 M Largest city in the
Caribbean by population Subject to severe
earthquakes Oldest European
settlement in the western hemispherehas been built and re-built,
streams re-directed, etc.
Area of metropolitan area is ~10 km x ~20 km.
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Figure from Bilham, Lessons from the Haiti earthquake, Nature
463, 878-879 (18 February 2010), doi:10.1038/463878a
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The toll of the 2010 Haiti quake is more than twice that of any
previous magnitude 7.0 event, and the fourth worst since 1900
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Seismic Microzonation
The process of subdividing potential earthquake prone area into
zones with respect to some geophysical characteristics of the sites
such as ground shaking, susceptibility to liquefaction, landslide
or rock fall hazard, or earthquake-related flooding, so that
seismic hazards at different locations within the area can be
correctly identified.
Site Characterization The process of estimating the response of
soil layers to earthquakes and thus the variation of earthquake
characteristics on the ground surface.
Provides the basis for site-specific risk analysis, which can
assist in the mitigation of earthquake damage.
A preliminary phase of earthquake risk mitigation studies.
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Methods
Dynamic characteristics of site such as predominant period,
amplification factor, shear wave velocity, standard penetration
test (SPT) values can be used for seismic microzonation
purposes.
Shear wave velocity measurements and standard penetration tests
are generally expensive and are not feasible to be carried out at
large number of sites for the purpose of microzonation
(active-source techniques).
Passive-source techniques can also be used to determine the
dynamic properties of soil strata. Measurements are easy to
perform, inexpensive, and can be carried out in places with low
seismicity rates.
Ambient noise (also called microtremor) analysis
Horizontal-vertical spectral ratio (HVSR) modeling (e.g.,
Nakamura, 1989)
Spatial autocorrelation (SPAC) array processing method (e.g.,
Asten, 2006)
F-k methods (e.g., Louie, 2001)
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Comparison of Methods
Table from Asten, M.W., and Boore, D.M., eds., Blind comparisons
of shear-wave velocities at closely spaced sites in San Jose,
California: U.S. Geological Survey Open-File Report 2005-1169.
[available on the World Wide Web at
http://pubs.usgs.gov/of/2005/1169/ ].
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Which method is best?
It depends on What information you need Which subset of
information you need to be most
reliable (e.g., average Vs, ability to resolve layering
(especially low-velocity layers), depth of penetration, systematic
bias if any in velocity estimates)
Logistics Funding limitations Skill sets and personnel available
Operational limitations (e.g., can you use active
sources?)
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Results
Table from Asten, M.W., and Boore, D.M., eds., Blind comparisons
of shear-wave velocities at closely spaced sites in San Jose,
California: U.S. Geological Survey Open-File Report 2005-1169.
[available on the World Wide Web at
http://pubs.usgs.gov/of/2005/1169/ ].
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800 Observation Points in Santo Domingo
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Logistics
Santo Domingos metropolitan area is ~10 km x ~20 km.
A grid in which observation points are spaced 500 m apart would
produce 800 observations points.
A team of two skilled people can make observations at 40 sites
in three days.
20 teams would be able to acquire all the data in three
days.
Alternatively (in order to reduce logistics of vehicles,
equipment, etc.), two groups of 10 teams could alternate tasks over
6 days: one group records data while the other group processes
data.
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Questions or Comments?
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SPAC
Elham Shabani, et al., 2011. The SPAC Method for a Finite
M-Station Circular Array Using Horizontally Polarized Ambient
Noise, Bulletin of the Seismological Society of America, Vol. 101,
No. 2, pp. 544557, April 2011, doi: 10.1785/0120090213
(a) SPAC coefficient obtained for vertical components of
microtremor records in the array; the black dots and error bars are
the samples selected. (b) The Rayleigh-wave dispersion curve.