1. EARTHQUAKE EFFECTS, PATTERNS, AND RISK

2. Earthquake Effects - Surface Faulting
Landers, CA 1992

3. Thrust Fault Example

4. Normal Fault Example Dixie Valley-Fairview Peaks, Nevada earthquake
December 16, 1954

5. Total Slip in the M7.3 Landers Earthquake
Rupture on a Fault
Total Slip in the M7.3 Landers Earthquake
Total distribution of slip after earthquake happened.
Red is a lot of slip, blue is no slip
You can see that the whole surface did not slip the same amount
Nor did it slip all at the same time, as you will see in this movie

6. Earthquake Effects - Ground Shaking
Northridge, CA 1994

7. Earthquake Effects - Ground Shaking
Loma Prieta, CA 1989
KGO-TV News ABC-7

8. NATURAL PERIOD OF BUILDINGS
Natural Period, T = 1/f
Typical values:
Stories: Value:
sec
10 1
20 2
30 3

9. Earthquake Effects - Ground Shaking
Kobe, Japan 1995

10. Earthquake Effects - Ground Shaking
Kobe, Japan 1995

11. TSUNAMIS
Earthquakes beneath the ocean floor sometimes generate immense sea waves, or tsunamis.
These waves travel across the ocean at speeds as great as kilometers per hour and may be 15 meters high or higher by the time they reach the shore.
During the 1964 Alaskan earthquake, tsunamis engulfing coastal areas caused most of the destruction at Kodiak, Cordova, and Seward and caused severe damage along the west coast of North America, particularly at Crescent City, California. Some waves raced across the ocean to the coasts of Japan.

12. Earthquake Patterns in Time and Space
Foreshock-main event-aftershock pattern: increase in number of microearthquakes in area of future rupture preceding a main event, and the decrease in earthquake activity after a main event
Quiescence: an anomalous loss of normal background microearthquakes for hours or days preceding a main event
Seismic Gaps: an absence of expected earthquakes on a segment of an active fault
Slip-rate diagrams: cumulative slip vs. time to estimate repeat times and average amounts of slip

13. EARTHQUAKE RISK ESTIMATES
To estimate the danger of destructive earthquakes in a region, a number of factors need to be assessed:
1) earthquake history--instrumental-- provides location, size, and timing of events in last 50 years
2) non-instrumental history-- provides location, estimated size (or at least damage), and timing
3) geologic history of fault movement at archeological sites and prior to human history.

14. PALEOSEISMOLOGY
The earthquake study will identify active faults, and the pattern of events. Patterns to examine include repeat times, amount of movement at each event, whether preceded by microearthquakes or other changes in terrain, water level, animal behavior, etc.

15. Prediction vs. Forecast

16. Prediction vs. Forecasting
PARAMETER PREDICTION FORECAST
LOCATION: +/- <5 km +/- 50km
TIME: +/- hours or days +/-decades to centuries
SIZE: +/- 1 Magnitude +/- 2 M

17. LOCATION
Seismologists use Instrumental Records of the arrival times of the P and S waves. Location quality has improved with more stations carefully calibrated, but can be as bad as +/- 50 km in some remote regions!
Paleo-seismologists use:
Historical Records
Geological Field Data: scarps, gouge, offsets, landslides, disturbed archaeological sites
Evidence of ancient tsunamis

18. Time
Seismologists use Instrumental Records. Can narrow the time down to a fraction of a second.
Paleoseismologists: dated historical records, isotopic dating of offset features. Some rock types are undatable for this purpose. Most radiometric dates are +/- 50 to 150 years.

19. Size
Seismologists: instruments. Depends on careful calibration. Can be accurate to 0.01 Magnitude units.
Paleoseismologists: estimates based on size of rupture zone (fractured rock), amount of slip, damage reports, how far inland and how high above sealevel tsunami deposits are found