The Earth is Moving! 123°W 122°W Longitude Latitude N ° 8 3 N ° 7 3 0 30 0 30 miles km major active faults other faults PACIFIC OCEAN San Francisco Bay San Francisco Santa Cruz Gilroy Monterey Farallon Islands Point Reyes San José Oakland Livermore Concord Santa Rosa Vacaville Vallejo Davis t l u a f s a e r d n A n a S t l u a f s a e r d n A n a S t l u a f s a e r d n A n a S t l u a f k e e r C s r e g d o R t l u a f e l l i v n e r G t l u a f d r o c n o C t l u a f d r a w y a H t l u a f a p a N t s e W y e l l a V n e e r G t l u a f t l u a f s a r e v a l a C t l u a f a t i l a g i t r O ½ inch per year 1 cm per year 210˚ 210˚ 240˚ 240˚ 270˚ 270˚ 300˚ 300˚ 330˚ 330˚ 360˚ 360˚ 30˚ 30˚ 60˚ 60˚ 90˚ 90˚ 120˚ 120˚ 150˚ 150˚ 180˚ 180˚ -60˚ -60˚ -30˚ -30˚ 0˚ 0˚ 5˚ 30˚ 30˚ 60˚ 60˚ Data from Kreemer et al. (2003), GSRM v. 1.2 North America North America Eurasia Arabia South America Africa (Nubia) Somalia Philippine Sea Nazca Cocos Scotia Caribbean Juan de Fuca Pacific Pacific Antarctic Antarctic India Australia Okhotsk Amuria ? White = Rigid Plates Red = Deforming zones between plates Grey = Plate names 2 inches (5 cm) per year velocities relative to Nubia San Andreas fault Step 1: Set up GPS antenna exactly over center of benchmark Step 2: Record the precise position using GPS instrument Scientists making measurements after the 1906 earthquake saw clear evidence that the earth moved during the earthquake. This fence was torn apart when the two sides of the fault moved relative to one another. Surveyors measure earth movement. Step 4: The position of the benchmark changed because the Earth’s crust has moved! Step 3: Repeat the process a few years later Survey benchmark GPS Antenna GPS Instrument 1998 37.93439377 °N 122.34002635 °W 2003 Latitude Year 37.93439322 °N Longitude 122.34002390 °W Which direction is this benchmark moving? How would you measure the slow movement of the Earth’s crust? Trying to measure this slow motion is like watching your finger nails grow. Scientists make the measurements using GPS (Global Positioning System) equipment -- the same technology used by hikers and rental car navigation units, but even more precise. Each arrow on the map represents several measurements of a single benchmark as much as a decade apart! 1998 1999 2001 2003 Stop on a dime: Scientific GPS instruments zero-in on position to within half the diameter of a dime! N S E W The earth moved along a fault during the 1906 earthquake The words “plate tectonics” did not come along for sixty more years, but we now know that the 1906 scientists discovered some of the first evidence of constant plate motions. The white portions of the map above are parts that move along as a big piece called a “plate.” When plates collide, the areas in red act like crumple zones in a car accident. We live right in the middle of one of these zones! After 1906, scientists recognized that the motion that continued after the earthquake would cause stress to build Early evidence for plate tectonics Plate motions cause earthquakes. San Francisco Bay Area in Motion Unlike during the earthquake, however, this later motion was not along the fault – the entire region was deforming. What were these scientists seeing? Scientists have been measuring the constant plate motion in the time between earthquakes so that they can determine the amount of strain that must be released in future Bay Area earthquakes. Average motion, 1993 - 2003, measured using high precision GPS. Arrows show the amount of motion relative to San Francisco Bay. There have been no major earthquakes during this time period, so almost all of the motion represents strain that has built up. Continued measurements showed the Earth continued to move – even in the years after the quake. What does this motion tell us about the way the Earth works? A new fence is built straight across the fault at the boundary between two plates. The cycle continues because plate motion plate motion continues. Over many years, plate plate motion motion causes strain to build up and deform the earth (and fence). An earthquake is a sudden burst of motion that relieves the strain and causes shaking. Before and After an Earthquake The Earthquake Itself up. Releasing that stress and strain is what causes earthquakes. ???????????????????????????????????????? ?????????? ???????????????????????????????????????? ?????????? How much closer does Santa Cruz get to San Francisco each year? How far has it moved since you were born? Fault The Bay Area deforms as strain builds up. arrows far from faults reveal plate motion Fremont Data from U. C. Berkeley, http://seismo.berkeley.edu/~burgmann/RESEARCH/BAVU/
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The Earth is Moving!
123°W 122°W Longitude
Latit
ude
N°83N°73 0 30
0 30
miles
km
major active faultsother faults
PACIFICOCEAN
SanFrancisco
Bay
SanFrancisco
SantaCruz
Gilroy
Monterey
FarallonIslands
PointReyes
SanJosé
Oakland
Livermore
Concord
SantaRosa
Vacaville
Vallejo
Davis
tluaf
saer
dnA n
aS
tluaf
saerd
nA n
aS
tluaf
saerd
nA n
aS
tluaf
keer
C sre
gdoR
tluaf
ellivn
erG
tluaf
droc
noC
tluaf
dr
awya
Htl
uaf
apaN
tse
W
yell
aV n
eerG
tlua
f
tlua
f sar
eval
aC
tluaf
atilagi
trO
½ inch per year1 cm per year
210˚
210˚
240˚
240˚
270˚
270˚
300˚
300˚
330˚
330˚
360˚
360˚
30˚
30˚
60˚
60˚
90˚
90˚
120˚
120˚
150˚
150˚
180˚
180˚
-60˚ -60˚
-30˚ -30˚
0˚ 0˚
5˚
30˚ 30˚
60˚ 60˚
Data from Kreemer et al. (2003), GSRM v. 1.2
NorthAmerica
North America
Eurasia
Arabia
SouthAmerica
Africa(Nubia)
Somalia
Philippine
Sea
Nazca
Cocos
Scotia
Caribbean
Juande Fuca
Pacific
Pacific
Antarctic
Antarctic
India
Australia
OkhotskAmuria ?
White = Rigid Plates Red = Deforming zones between platesGrey = Plate names 2 inches (5 cm) per year
velocities relative to Nubia
San Andreas fault
Step 1:Set up GPS antenna exactly over center of benchmark
Step 2:Record the precise position using GPS instrument
Scientists making measurements after the 1906 earthquake saw clear evidence that the earth moved during the earthquake.
This fence was torn apart when the two sides of the fault moved relative to one another.
Surveyors measure earth movement.
Step 4:The position of the benchmark changed becausethe Earth’s crust has moved!
Step 3:Repeat the process a few years later
Surveybenchmark
GPS Antenna
GPS Instrument
199837.93439377 °N 122.34002635 °W2003
LatitudeYear37.93439322 °N
Longitude122.34002390 °W
Which direction is thisbenchmark moving?
How would you measure the slow movement of the Earth’s crust?Trying to measure this slow motion is like watching your finger nails grow. Scientists make the measurements using GPS (Global Positioning System) equipment -- the same technology used by hikers and rental car navigation units, but even more precise.
Each arrow on the map represents several measurements of a single benchmark as much as a decade apart!
1998 1999
2001 2003
Stop on a dime: Scientific GPS
instruments zero-in on position to within
half the diameter of a dime!
N
SS
EEWW
The earth moved along a faultduring the 1906 earthquake
The words “plate tectonics” did not come along for sixty more years, but we now know that the 1906 scientists discovered some of the first evidence of constant plate motions.
The white portions of the map above are parts that move along as a big piece called a “plate.” When plates collide, the areas in red act like crumple zones in a car accident. We live right in the middle of one of these zones!
After 1906, scientists recognized that the motion that continued after the earthquake would cause stress to build
Early evidence for plate tectonics
Plate motions cause earthquakes.
San FranciscoBay Area in Motion
Unlike during the earthquake, however, this later motion was not along the fault – the entire region was deforming. What were these scientists seeing?
Scientists have been measuring the constant plate motion in the time between earthquakes so that they can determine the amount of strain that must be released in future Bay Area earthquakes.
Average motion, 1993 - 2003,measured using high precision GPS.
Arrows show the amount of motion relative to San Francisco Bay. There have been no major earthquakes during this time period, so almost all of the motion represents strain that has built up.
Continued measurements showed the Earth continuedto move – even in the yearsafter the quake.
What does this motion tell usabout the way the Earth works?
A new fence is built straight across the fault at the boundary between two plates.
The cycle continues because plate motionplate motion continues.
Over many years, plate plate motionmotion causes strain to build up and deform the earth (and fence).
An earthquake is a sudden burst of motion that relieves the strain and causes shaking.
Before and After an Earthquake The Earthquake Itself
up. Releasing that stress and strain is what causes earthquakes.
??????????????????????????????????????????????????????????????????????????????????????????????
????
??
How much closer does Santa Cruz get to San Francisco each year?
How far has it moved since you were born?
Fault
The Bay Area deforms as
strain builds up.
arrows far from faults
reveal plate
motion
Fremont
Data from
U. C
. Berkeley, http://seism
o.berkeley.edu/~burgm
ann/RE
SE
AR
CH
/BA
VU
/
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