Can We Predict Earthquakes?

- Andrea Nemeth
- Advisor Dr. Mark Schilling

Earthquake Prediction

- location
- time
- magnitude
- probability of
- occurrence
- reliable
- accurate

The collapse of part of Jefferson Junior High

School in Long Beach in 1933.(Photo Portland

Cement Association)

Methods Employed In Earthquake Prediction

- statistical probability
- physical measurements
- geochemical observations
- observations of animal behavior

Seismicity of California (USGS)

Real Data or Simulated?

Popular media statements

- the Big One is overdue
- the longer it waits, the bigger it will be

(USGS)

Statistical Models

- time-independent
- Poisson (exponential)
- model
- time-dependent
- Gaussian
- gamma
- log-normal
- Weibull distributions
- Brownian Passage
- Time

Poisson Model Weibull Model

- Magnitudes of EQs and the time intervals between

EQs are each assumed to be independently

distributed. - memoryless

- The probability of rupture is a function of the

accumulated strain.

Parkfield and Wrightwood

- Parkfield area
- medium-sized EQs occur here fairly regularly
- Wrightwood area
- long term data is available

LA

(USGS)

The Experiment

- 1857, 1881, 1901, 1922, 1934, 1966
- USGS prediction
- an earthquake of M6 would occur in Parkfield

between 1983 and 1993

So how regular are the recurrence times of these

earthquakes?

The intervals between these EQs 24, 20, 21, 12,

32, 38

- Mean
- 24.5 years
- Standard deviation
- 9.25 years.

Probability Plots

Can we rule out the possibility that even EQs at

Parkfield are random in time?

24 7 3 10 25 31

20 20 25 29 7 53

21 4 5 27 20 5

12 13 9 7 47 18

32 17 16 32 2 22

38 11 41 27 39 12

9.25 5.79 14.59 10.63 17.75 16.93

- Result 8.8 of all simulated interval sequences

had standard deviation less than 9.25. - Conclusion
- This sequence is somewhat regular, but not

extremely unusual.

Wrightwood

534, 634, 697, 722, 781, 850, 1016, 1116, 1263,

1360, 1470, 1536, 1610, 1690, 1812, 1857

The Recurrence Times of the EQs at Wrightwood

- The time intervals between successive EQs
- 100, 63, 25, 59, 69, 166, 100, 147, 97, 110, 66,

74, 80, 122, and 45 years. - mean
- 88.2 years
- standard
- deviation
- 37.8 years.

Probability Plots

Simulation for the Wrightwood area

- Result
- Only 1.5 of all simulated interval sequences

had standard deviation less than 37.8 years. - Conclusion
- This sequence of 16 EQs at Wrightwood is more

regular than the Parkfield sequence.

Summary

- Several factors make EQ prediction difficult
- the cycle of EQs is long
- the fundamental physics of EQ faulting is not yet

understood - no clearly recognizable precursor has been

observed - EQ history is short for most faults

Potential Future Work

- Further investigation of the Wrightwood data
- Analysis of other data sets from the
- San Andreas Fault
- Study of other statistical models with our data

Acknowledgments

- This project was sponsored by the NASA/JPL PAIR

program. - I thank Dr. Carol Shubin for her continuous

support, interest and encouragement. - Im very grateful to Dr. Mark Schilling, my

advisor, for his comments on the data analysis

and preparation, for his valuable insights

andobservations.