Lesson 1 Flashcards
produced by sudden movement of rock materials below the earths surface
earthquake
2 types of earthquake
tectonic earthquake
volcanic earthquake
movement along faults and plate boundaries
tectonic earthquake
induced by rising lava/magma beneath active volcanoes
volcanic earthquake
theory that explains the formation and deformation of the earths surface
Plate Tectonics Theory (1960)
earths outermost layer is divided into ___ major tectonic plates
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Evidence for continental drift
matching coastlines
matching mountains
matching rock types and rock ages
matching glacier deposits
matching fossils
symptoms of active tectonic movements and as observed that the intense activity occurs predominantly on plate boundaries (seismic belts)
earthquake
large and stable rigid rock slabs with a thickness of about 100 km forming the crust and part of the upper mantle
plates
outer rock layer with non-uniform thickness of 25-60 km under the continents and 4-6 km under oceans
crust
portions of the earths interior below crust extending from 30 km - 2900 km
mantle
____ causes movement in the mantle with 1 to 10 cm/year
convection currents
Types of plate boundaries
divergent/rift zones
convergent/subduction zones
transform zones/transcurrent horizontal slip
plates separated by effusion of magma occurence; formation of mid-ocean ridge (Mid-Atlantic Ridge)
divergent/rift zones
adjacent plates collide; plates come together
convergent/subduction zones
two plates glide past one another but without subducting old lithosphere; plates slides past each other
transform zones/transcurrent horizontal slip
distorted blocks snaps back toward equilibrium and an earthquake ground motion is produced; AKA elastic rebound
faulting
resulting fracture in the earths crust
fault
rocks bend under stress while storing elastic energy. when the strain in the rocks exceeds their strength, breaking will occur along the fault.
elastic rebound theory
parameters used to describe fault motion and its dimension
azimuth
dip
slip/rake
relative displacement
area
one block moves away vertically with respect to the other; footwall moves up the dip and away from the block overhanghing the fault plane
dip-slip faults
adjacent blocks move horizontally past one another; can be right-lateral or left-lateral
strike-slip faults
combination of strike-slip and dip slip movements; can either be normal or reverse and right or lefr lateral movements
oblique slip
point under the surface where the rupture originates
focus/hypocenter
projection of the focus on the surface
epicenter
source parameters
epicentral distance
hypocentral/focal distance
focal depth
2 types of elastic seismic waves
body waves
surface waves
aka ‘preliminary tremors’ because they are felt first and travels through the earths interior layers
body waves
cause alternate push (compression) and pull (tension) in the rock thus the waves propagates, the medium expands while keeping the same form
p-waves
material movement is the same direction as wave movement
p-waves
causes vertical and horizontal side-to-side motion and introduces shear stresses in rocks along their paths aka shear waves
s-waves
motion can be separated into horizontal and vertical components
s-waves
propagate across the outer layers of the crust generated by constructive interference of body waves travelling parallel to the ground surface and various underlying boundaries
surface waves
slower than body waves; rolling side to side movements
surface movements
generated by constructive interference of SH body waves and cannot travel across fluids
love waves
the motion is horizontally oscillating and perpendicular to the direction of propagation which is parallel to the earths surface
love waves
caused by constructive interference of body waves such as P and SV
rayleigh waves
particles of soil move in the form of a retrograde ellipse whose axis is perpendicular/vertically oscillating to the earths surface;
rayleigh waves
causes back and forth horizontal motion; motion is similar to that of being in a boat in the ocean; arrive last on seismogram
rayleigh waves
visual record of arrival time and magnitude of shaking associated with seismic wave
seismogram
adjustments that follow a major earthquake often generate smaller earthquake
aftershocks
small earthquakes often precede a major earthquake by days or by as much as several years
foreshocks
