9.7 predicting quakes

goal of short range predictions

provide warning of location and magnitude within short time frame

precursors to quakes:

monitor changes in ground elevation, measure strain in rocks

measure changes in groundwater level

frequency of foreshocks

anomalous animal behavior (very unrealistic)

why are short-range predictions still in their early days?

no reliable method for making short-range quake rpedictions

in order for prediction scheme to be accepted, must have small range of uncertainty for locartion & timing, must produce few failures or false alarms

what is the goal of long range forecasts

estimate how likely for an earthquake of certain magnitude to cocur in 10-30 years

what are large range forecasts based on?

earthqaueks repetivie/cyclical, use historical records, or plaeoseismology

why are long range forecasts important?

provide uniform building code, assist in land use planning

seismic gap

long range prediction, section of active fault without major earthquake in a centiry or more, probable site for future major quakes

paleoseismology

studt of timing, location, and size of prehistoric quakes

paleoseismology studies

conducted by digging trench across suspected fault zone and looking for evidences of displacement: large vertical offset of sediment layers likely means large quake

plant debris

used to date prehistoric or older quakes

san andreas paleoseimoologyu

pallet creek disturbed by ruptures, stroke quakes once every 135 years, cyclic quakes means 1857 to now its due for another quake