earthquakes reflection 4- margin earthquakes

ocean-ocean convergence

older, cooler, denser subducts, chain of volcanic islands on other plate, produces zone of progressively deeper earthquakes

ocean-continental convergence

oceanic subducts, mountains or volcanoes forms on continental, shallow to deep earthquakes, most population

continental-continental convergence

high mountain ranges, no subduction, no volcanoes, shallow, damaging earthquakes

megathrust earthquakes

rupture at contact between subducting and overriding plate, largest, tsunamis, most dangerous

assam-tibet earthquake

largest continental-continental quake

convergent boundary stress

compression, thrust faulting, adding and resisting friction

divergent boundary stress

tensional stress, normal faulting, shallow earthquake

horst and graben structure

series of normal faults, alternating valleys and ridges

basin and range

rift valleys in western us, shallow earthquakes, normal faults where they switch from basin to range

transform boundary stress

shear stress, slide past, parallel to boundary, strike slip faults, shallow earthquakes

seismic gaps

lengths of active faults that experience few earthquakes, strain can build to a big quake, useful for earthquake probability

earthquake sequence

releases strain where fault ruptures, stress moved to locked section, stress builds, may be site of next quake, may move in sequence along fault

aseismic creep

slow, continual fault movement with no notable earthquakes, water and mud can lessen friction, less risk, less stress

intraplate earthquake features

colder, more rigid, continuous, seismic waves lose less energy within plates, felt over larger areas, not predictable

hotspot intraplate earthquake

upwelling mantle pushes upward, growing volcanoes push downward, differential stress, rising hot material distorts material above it

other factors for intraplate earthquakes

old plate boundaries, isostatic rebound, failed rifts

isostatic rebound

ice sheets add mass to continents, ice melts, mass removed, changes stress applied to crust, differential stress

failed rifts

divergent boundary starts to rift on continental crust, rifting stops, gets buried under sediment, zone of weakness

__ of top 10 largest quakes since 1900 occurred at subduction zones

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induced seismicity

triggered by human activity, loads crust, changes stress, lubricates faults