1. Seismic Hazard Assessment for the Kingdom of Saudi Arabia
Tom Brocher
Director, Earthquake Science Center
U.S. Geological Survey
June 1, 2014

2. The Goal
Provide a state-of-the-art seismic hazard assessment for the Kingdom
Focus on characterizing earthquake faults within the Kingdom – earthquake chronology, slip per event, slip rates, magnitudes, style of faulting
Another focus will be ground motion prediction equations and site response within the Kingdom
Assessing extreme wave hazard along the coasts
Training is a major goal of the work

3. Characterizing Earthquake Faults
Identifying and mapping young faults
Quaternary Geologic maps
Photos and Imagery
LiDAR
InSAR
Aeromagnetic mapping
Seismic reflection profiling

4. Characterizing Earthquake Faults
Conducting field and laboratory studies of faults
Field mapping
Geomorphic analysis
Trenching
Age dating of offset soils

5. Predicting Strong Ground Motions
Compile existing strong ground motion data within the Kingdom and nearby regions
Derive ground motion prediction equations
Characterize crustal structure to regionalize the ground motion data
Characterize site response (Vs30) in the Kingdom
Imaging sedimentary basins for long period response

8. Characterize strain rates in the Kingdom
Use GPS and InSAR data to estimate strain rates in the Kingdom
Compile earthquake catalog and generate a smoothed seismicity map for the Kingdom

9. PSHA Analysis Earthquake faults Smoothed seismicity Strain rates
Ground motion predictions
Site response (Vs30)
Pascucci, Free, Lubkowski, 2008

10. Who are we?
The Earthquake Science Center has many years of experience performing seismic hazard assessments in California and the US
Expertise in:
Paleoseismic investigations of faults
Geophysical characterization of faults
Prediction of strong ground motions
Geodesy and strain measurements
Earthquake monitoring
Probabilistic Seismic Hazard Analysis

13. Earthquake Science Center Organization
Earthquake Monitoring (53 staff)
Earthquake Monitoring Project (28 staff)
Southern California Seismic Network (14 staff)
Deformation (13 staff)
Earthquake Hazard Assessment (48 staff)
Shaking, Damage, Failure (Earthquake Effects) (20 staff)
Southern California Earthquake Hazards Assessment (11 staff)
Pacific Northwest Hazards Project (10 staff)
Bay Area Earthquake Hazards (7 staff)
Earthquake Research (22 staff)
Earthquake Processes Probabilities and Occurrence (13 staff)
Induced Seismicity (9 staff)

14. Hazard Methodology Procedure Cartoon
The first step in making hazard maps: construct a hazard curve at each site
Hazard Methodology Procedure Cartoon a
Earthquake Sources b a
Ground motion
Hazard curve r1
M 7.6 d1 d4
annual probability of exceeding pga r2 d2
peak ground acceleration
M7.6 d3
high seismicity
zone
San Andreas fault
distance
0.25g
0.5g
peak ground acceleration (pga) r3

15. Constructing a hazard curve: a real example
1/200=0.005
Source B
M7.5, Tr=200 yr
50km
10km
Site
Source A
M5.5, Tr=10 yr
1/10=0.10
Annual probability that earthquake occurs:
Source A: 1/10 = 0.10
Source B: 1/200 = 0.005

16. Consider the uncertainty in motions from GMPEs

17. Consider the uncertainty in motions from GMPEs

18. Combine the source and ground-motion uncertainties

19. Plot the resulting FOE for the PSA value

20. Do this for all possible ground motions from Source A to make a hazard curve for Source A

21. Combine hazard curves for all source t make the final hazard curve

22. Pick off value for hazard map

23. Make a map of the ground-motion values for a given FOE; this is the hazard map that is the basis for the design maps included in building codes

27. Note: different M and R limits than on slide for Anchorage

30. Interferograms Used Spokane, Washington
Interferogram 1 and 2 are from the ERS-2 satellite. Interferograms 3-5 are from the RADARSAT-1 satellite. Interferogram 6 is from the ENVISAT satellite.
DEM is from SRTM, used in topographic corrections.
Satellite flight direction labeled AZ, look direction labeled LOS. 4

31. We invert for the Vertical and East components of deformation using the interferograms (2-5) shown in the previous slide.
The freeway (I 80) and major US routes (2 and 395) are shown in each panel. The city streets are shown in the top panel. 5

32. Comparison of best-fit model to data
Cross-section A-A’ and B-B’ shown in next slide. 8

33. Comparison of best-fit model to data – Cross-Sections9

34. Model fault line in downtown Spokane, GoogleEarth
Hanging-wall is on the left and Foot-wall is on the right.
Spokane was a Native American meeting place because of the Falls.
Europeans were attracted to Spokane because of the Falls.
Spokane was founded in 1873 as the city of Spokane Falls.
After the Spokane Fire of 1889 destroyed the downtown, wooden buildings were prohibited during the rebuild.
From historicalspokane.org: “Spokane's rebirth resulted in about 100 new elaborate brick, masonry, and terra cotta commercial buildings in the downtown in the year immediately following the fire.”
Over 50% of the buildings in Spokane are designated historic, many of them brick buildings built just after the fire.
Looking NE 11