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![Page 1: Bill Ellsworth U.S. Geological Survey Near-Source Observations of Earthquakes: Implications for Earthquake Rupture and Fault Mechanics JAMSTEC International.](https://reader035.fdocuments.in/reader035/viewer/2022062801/56649e7e5503460f94b81f23/html5/thumbnails/1.jpg)
Bill Ellsworth
U.S. Geological Survey
Near-Source Observations of Earthquakes:Implications for Earthquake Rupture and Fault
Mechanics
JAMSTEC International Technical Committee on Long Term Monitoring System Development for Ocean Boreholes
Yokohama, Japan February 16-17, 2009
![Page 2: Bill Ellsworth U.S. Geological Survey Near-Source Observations of Earthquakes: Implications for Earthquake Rupture and Fault Mechanics JAMSTEC International.](https://reader035.fdocuments.in/reader035/viewer/2022062801/56649e7e5503460f94b81f23/html5/thumbnails/2.jpg)
A central goal of seismology is to understand the physical conditions under which earthquakes occur
Key question seismology can address inthe near-source region include:
• Minimum size of earthquakes• Magnitude dependence of source parameters• Rupture nucleation• Stress evolution during and following rupture
rD
Illustrations by Peter Shearer
![Page 3: Bill Ellsworth U.S. Geological Survey Near-Source Observations of Earthquakes: Implications for Earthquake Rupture and Fault Mechanics JAMSTEC International.](https://reader035.fdocuments.in/reader035/viewer/2022062801/56649e7e5503460f94b81f23/html5/thumbnails/3.jpg)
A central goal of seismology is to understand the physical conditions under which earthquakes occur
Key question seismology can address inthe near-source region include:
• Minimum size of earthquakes• Magnitude dependence of source parameters• Rupture nucleation• Stress evolution during and following rupture
u(t).
σd
Dc
ES
![Page 4: Bill Ellsworth U.S. Geological Survey Near-Source Observations of Earthquakes: Implications for Earthquake Rupture and Fault Mechanics JAMSTEC International.](https://reader035.fdocuments.in/reader035/viewer/2022062801/56649e7e5503460f94b81f23/html5/thumbnails/4.jpg)
A central goal of seismology is to understand the physical conditions under which earthquakes occur
Key question seismology can address inthe near-source region include:
• Minimum size of earthquakes• Magnitude dependence of source parameters• Rupture nucleation• Stress evolution during and following rupture
.
σd
Dc
ES
![Page 5: Bill Ellsworth U.S. Geological Survey Near-Source Observations of Earthquakes: Implications for Earthquake Rupture and Fault Mechanics JAMSTEC International.](https://reader035.fdocuments.in/reader035/viewer/2022062801/56649e7e5503460f94b81f23/html5/thumbnails/5.jpg)
Shaking Forecast Model
![Page 6: Bill Ellsworth U.S. Geological Survey Near-Source Observations of Earthquakes: Implications for Earthquake Rupture and Fault Mechanics JAMSTEC International.](https://reader035.fdocuments.in/reader035/viewer/2022062801/56649e7e5503460f94b81f23/html5/thumbnails/6.jpg)
World-wide Strong Motion Data Set(as of 2004)
![Page 7: Bill Ellsworth U.S. Geological Survey Near-Source Observations of Earthquakes: Implications for Earthquake Rupture and Fault Mechanics JAMSTEC International.](https://reader035.fdocuments.in/reader035/viewer/2022062801/56649e7e5503460f94b81f23/html5/thumbnails/7.jpg)
2002 M 7.9Denali Earthquake
Near-Field Ground Motion at
Pump Station 10
East (km)
Nort
h (
km)
-20 -10 0 10 20
-20
-10
010
20
1 m
![Page 8: Bill Ellsworth U.S. Geological Survey Near-Source Observations of Earthquakes: Implications for Earthquake Rupture and Fault Mechanics JAMSTEC International.](https://reader035.fdocuments.in/reader035/viewer/2022062801/56649e7e5503460f94b81f23/html5/thumbnails/8.jpg)
Accelerations were modest (0.36 g)Acc
ele
ration
(cm
/sec^
2)
-300
-100
100
300
Acc
ele
ration
(cm
/sec^
2)
-300
-100
100
300
Seconds
Acc
ele
ration
(cm
/sec^
2)
-300
-100
100
300
0 20 40 60 80
Fault Normal
Fault Parallel
Vertical
![Page 9: Bill Ellsworth U.S. Geological Survey Near-Source Observations of Earthquakes: Implications for Earthquake Rupture and Fault Mechanics JAMSTEC International.](https://reader035.fdocuments.in/reader035/viewer/2022062801/56649e7e5503460f94b81f23/html5/thumbnails/9.jpg)
Velo
city
(cm
/s)
-100
050
100
200
Velo
city
(cm
/s)
-100
050
100
200
Seconds
Velo
city
(cm
/s)
-100
050
100
200
0 20 40 60 80
Velocities were pulse-like (180 cm/s)
East (cm/s)
Nort
h (
cm/s
)
-100 -50 0 50 100 150 200
-15
0-1
00
-50
050
100
150
1718
1920
21
22 2324
25
Fault Normal
Fault Parallel
Vertical
![Page 10: Bill Ellsworth U.S. Geological Survey Near-Source Observations of Earthquakes: Implications for Earthquake Rupture and Fault Mechanics JAMSTEC International.](https://reader035.fdocuments.in/reader035/viewer/2022062801/56649e7e5503460f94b81f23/html5/thumbnails/10.jpg)
Displacements were geodetic (2.8 m)
Dis
pla
cem
en
t(cm
)
-20
0-1
00
01
00
20
0
Dis
pla
cem
en
t(cm
)
01
00
20
03
00
Seconds
Dis
pla
cem
en
t(cm
)
-10
00
10
02
00
30
0
0 20 40 60 80
East (cm)
Nort
h (
cm)
0 100 200 300
-20
0-1
00
01
00
200
17 18
1920
21
22
2324
25
Fault Normal
Fault Parallel
Vertical
![Page 11: Bill Ellsworth U.S. Geological Survey Near-Source Observations of Earthquakes: Implications for Earthquake Rupture and Fault Mechanics JAMSTEC International.](https://reader035.fdocuments.in/reader035/viewer/2022062801/56649e7e5503460f94b81f23/html5/thumbnails/11.jpg)
Where Does the Energy Come From?
Isochrones and Fault Parallel Displacement Intensity for Pump Station 10
0 . 00
0 . 05
0 . 10
0 . 15
0 . 20
0 . 25
* 1 0 * *0
- 60 - 40 - 20 0 20 40
DISTANCE ALONG STRIKE, KM
2.0
4.0
6.0
8.0
10
.0D
ISTA
NC
E D
OW
N D
IP,
KM
- 60 - 40 - 20 0 20 40
DISTANCE ALONG STRIKE, KM
2.0
4.0
6.0
8.0
10
.0D
ISTA
NC
E D
OW
N D
IP,
KM
30 .
30 .
30 .
35 .
35 .
35 .
40 .
40 .
40 .
45 .
45 .
45 .
50 .
50 .
50 .
55 .
55 .
55 .
60 .
60 .
60 .
65 .
65 .
65 .
0 . 0
0 . 1
0 . 2
0 . 3
0 . 4
0 . 5
0 . 6
* 1 0 * *0
- 60 - 40 - 20 0 20 40
DISTANCE ALONG STRIKE, KM
2.0
4.0
6.0
8.0
10
.0D
ISTA
NC
E D
OW
N D
IP,
KM
- 60 - 40 - 20 0 20 40
DISTANCE ALONG STRIKE, KM
2.0
4.0
6.0
8.0
10
.0D
ISTA
NC
E D
OW
N D
IP,
KM
30 .
30 .
30 .
35 .
35 .
35 .
35 .
40 .
40 .
40 .
45 .
45 .
45 .
50 .
50 .
50 .
55 .
55 .
55 .
60 .
60 .
60 .
Note change in scale
![Page 12: Bill Ellsworth U.S. Geological Survey Near-Source Observations of Earthquakes: Implications for Earthquake Rupture and Fault Mechanics JAMSTEC International.](https://reader035.fdocuments.in/reader035/viewer/2022062801/56649e7e5503460f94b81f23/html5/thumbnails/12.jpg)
How high are the stresses that cause big earthquakes?
![Page 13: Bill Ellsworth U.S. Geological Survey Near-Source Observations of Earthquakes: Implications for Earthquake Rupture and Fault Mechanics JAMSTEC International.](https://reader035.fdocuments.in/reader035/viewer/2022062801/56649e7e5503460f94b81f23/html5/thumbnails/13.jpg)
San Andreas Fault Observatory at Depth(SAFOD)
![Page 14: Bill Ellsworth U.S. Geological Survey Near-Source Observations of Earthquakes: Implications for Earthquake Rupture and Fault Mechanics JAMSTEC International.](https://reader035.fdocuments.in/reader035/viewer/2022062801/56649e7e5503460f94b81f23/html5/thumbnails/14.jpg)
Increase in Least Principal Stress Observed in the San Andreas Fault Zone
SAFOD
Stress Magnitudes: Pilot Hole, SAFOD
SV
Lithostat
![Page 15: Bill Ellsworth U.S. Geological Survey Near-Source Observations of Earthquakes: Implications for Earthquake Rupture and Fault Mechanics JAMSTEC International.](https://reader035.fdocuments.in/reader035/viewer/2022062801/56649e7e5503460f94b81f23/html5/thumbnails/15.jpg)
SAFOD Seismic SensorsCommercial high-frequency borehole seismometers
(Oyo Geospace DS150 – 150 C rating)
MEMS accelerometers replace geophones for broad band response
![Page 16: Bill Ellsworth U.S. Geological Survey Near-Source Observations of Earthquakes: Implications for Earthquake Rupture and Fault Mechanics JAMSTEC International.](https://reader035.fdocuments.in/reader035/viewer/2022062801/56649e7e5503460f94b81f23/html5/thumbnails/16.jpg)
Static Stress Drop Measurements at SAFOD
Hickman & Zoback (2004)
Average value is near the strength of the rock.
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Parkfield MainshockObserved on the Pilot Hole Array
2 seconds
P
S
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2004 Parkfield Main Shock and Early Aftershocks
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4 Minutes of Aftershocks of 2004 Parkfield Earthquake
![Page 20: Bill Ellsworth U.S. Geological Survey Near-Source Observations of Earthquakes: Implications for Earthquake Rupture and Fault Mechanics JAMSTEC International.](https://reader035.fdocuments.in/reader035/viewer/2022062801/56649e7e5503460f94b81f23/html5/thumbnails/20.jpg)
World-wide Strong Motion Data Set(as of 2004)
![Page 21: Bill Ellsworth U.S. Geological Survey Near-Source Observations of Earthquakes: Implications for Earthquake Rupture and Fault Mechanics JAMSTEC International.](https://reader035.fdocuments.in/reader035/viewer/2022062801/56649e7e5503460f94b81f23/html5/thumbnails/21.jpg)
World-wide Strong Motion Data Set(as of 2004)
NanTroSEIZE?