elastic reboudn theory
relative motion across a fault locked by friction actumulates elastic stress in the form of deformation. when the stress exceed the friction the fault slips and reases the energy as a sepctra of siesmic waves
what is the wave trend with increaign magnitudfe of EQs
greater energy in longer wavelength waves
Ritcher magnitude
first magnitude scale built for california. used for a wood anderson seismograph at 100 km form the epicenter
EQ Magnitude scale
attempts to quantify the energy released by and EQ Objective measure
limits of wood anderson
its sensitive to high frequency p waves(high absorbtion and spreading) so its not good for long distances or small EQs
suface wave magnitude
good for long distances and long wave length rayleih waves at distances greater than 2000 km form the epicenter
problem of surface wave mag
not good for deep eqs bc Raylieh waves are poorlh generated
what role do the contastants play in the formulas
various factors calibrate the scales so they are approximately the same when they apply
what problem arrises from EQ scales that are based on fixed periods
for large EQ the scales can saturate meaning they do not “see” what thier max calibration is
moment magnitude
relates to the fundimental properties of the source and therefore does not have saturate
how is moment magnitude determined
from studyign the source/ or with spectral analysis of long period waves
Gutenberge ritcher relation
the frequecy of en EQ above a given magnitude deacreases logrythmicly with magnitude
used to predicit the occarance of Large EQ when no have been observed usighn the occarfence of smaller EQS
magnitude energy relationship
energy increases exponentially with magnitude many small EQ will not substanitally reduce the hazard of a large EQ
MMI
intensity based onbserved affects, subjective measure at a location
Intestiy increases with what factors
proximity to the EQ, Magnitude of the EQ, loose soils compared to bedrock
Hyposcenter vs epicenter
hypo is a 3d location while the epicmnter is the location on the surface of the earth
how to locate local EQ
within 100km where vp and vs are known and approximatly constant so with can use the arrival tiem difference adn velocities to find the distance. we use Equation of circles with the distance as the radius to find the epicneter. we can also do this graphicly
Distannt EQs
Velocity are no longer constant and therefore we need to use time distance curves that are calculated by refference velocity modles to find the the Distance using the s p tiem diffrence. velocity
PcS and SKP
SKiKS SKIKS SKiKP
sPP
P S K I J c i p s LR LQ define each
what does recoding teh arrival times of siesmic waves tell us about the internal structure of the earth
earth is not uniform
Pwave shadow zone-low velocity outer core
swave shadow zone-liquid outer core
forward and invers modlign of travel times give us a radial siemic velityu modle of the earth