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GEOL 2390 Study Guide - Sea Level Rise, Shear Modulus, Bulk Modulus


Department
Geological Sciences
Course Code
GEOL 2390
Professor
William M.Last

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Introduction to Environmental Geology and class expectations
GEOPHYSICAL TOOLS
Remember - increasing costs
thus, use only after regional use of topi, geol maps etc
(almost) always on local scale
Mainly
seismic
most widely used
e.g. depth of bedrock
gravity
magnetics
basics:
apply sudden pressure to surface
disturbance (pressure) moves outwards from point of impact/source in form of
waves
velocity of a wave
density
elastic properties of material
V = (k +4/3 mu)/p
V = velocity of wave
k = bulk modulus resistance to change in volume
mu = shear modulus resistance to change in shape
p = density
low V material over high V material
why? density.
other (non-horizontal) waves reach interface and can travel along interface but con-
trolled by higher velocities
while travelling, continuous refraction up
eventually a geophone will record refraction wave 1st (before slower-moving hori-
zontal wave)
plot time of arrival vs. distance
slope of first few points - define V1
break in slope = critical distance (Cd)
distance where waves going through V1 and waves going through v1 - V2
- V1 arrive at same time
Depth = (Cd/2) [(V2-V1)/(V2+V1)]^0.5
not strictly hazards course but ~40% of time
most dramatic/awesome/spectacular
significant 4 - 'headline' catchers
hazard types
endogenic hazards - 'internal' earth processes
ground shaking
surface faulting
eq - induced ground failures, subsidence
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