lecture 5 Flashcards
surface ruptures
generated by large earthquakes which indicate slip has occured along linear faults
earthquake faulting
doesnt occur at points or lines
- instead are planar and show striations indicating directions
3 types of faulting involved in earthquakes
- reverse or thrust
- normal
- strike slip
- reverse or thrust faults
due to horizontal compressive stress
- one side thrsut over other and leads to shortening and crustal thickening
ASSOCIATED WITH CONVERGENT PLATE BOUNDARIES:
- subduction zones and continental collision zones
fault scarp
caused by thrust overhang collapse of a thrust fault
ex. raising the himalayas
fault planes
around 15km depth
only part of crust to cool enough to be brittle
rupture area
part of the fault plane that slips in the earthquake
surface rupture
where the rupture area intersects the surface
hypercenter
point on fault plane where slip starts
- normal faults
rupture due to horizontal tension stress, one side slides down the other and blocks move apart
leads to extension and crustal thinning
ASSOCIATED WITH DIVERGENT PLATE BOIUNDARIES: mid ocean ridges and continental rifts
- strike-slip faults
rupture due to simple shear, two sides move laterally past one another causing shortening in one direction and extension in another (no crustal thickening or thinning)
left lateral or right lateral
ASSOCIATED WITH STRIKE-SLIP PLATE BOUNDARIES: oceanic transform faults and continental shear zones
oblique faulting
many faults have a component of reverse or normal slip and a component of strike slip
earthquake cycle
stick-slip behavior: fault stuck between earthquakes until stress overcomes friction and sides slip
- driven by plate tectonics released by an earthquake in a few seconds
interseismic period
during earthquake cycle: steady motion occurs away from the fault but fault itself is locked (fence warps)
can be tracked using GPS
coseismic phase
marked by earthquake, elastic rebound returns fence A to linear but offsets at fence B and warps away
