Chapter 16 Geology
Modified Mercalli Scale
a 12 point scale developed to evaluate earthquake intensity based on the amount of damage to various structures
travel-time curve
a graph that plots the time since an earthquake began on the vertical axis and the distance to the epicenter on the horizontal axis
Intensity
a measure of an earthquakes effect on people and buildings
focus
the point within Earth where the segment waves first originate
Epicenter
this is the point on the surface of the Earth directly above the focus, where seismic waves are the strongest.
P Wave (Compressional)
wave in which rock vibrates back and forth parallel to the direction of wave propagation. very fast wave that arrives first
how do earthquakes cause tsunamis
-The rupture of the earthquake causes the seafloor to uplift water.
Name the various types of seismic wave
1. Body wave 2. Surface wave
describe some earthquake precursors, and predictions
1. cracks open within the rock 2. changes in magnetism 3. changes in electrical resistivity 4. seismic velocity
Describe five ways that earthquakes can cause damage
1. ground movement 2. fire 3. ground failure 4. aftershock 5. tsunami
minimum number of seismic stations needed to determine the location of the epicenter
3
Seismograph
A device that records ground movements caused by seismic waves as they move through Earth
Tsunami
A giant wave usually caused by an earthquake beneath the ocean floor.
S wave
A seismic wave propagated by a shearing motion, which causes rock to vibrate perpendicular to the direction of wave propagation.
Mediterranean-Himalayan belt
Approx 15% of all earthquakes occur here. Plate movement in this belt led to the formation of the Himalayan Mountains.
Benioff Zone
Benioff zones slope under a continent or a curved line of islands called an island arc
depth of focus
Distance between the focus and the epicenter of an earthquake.
the point within earth where seismic waves originate is called the
Focus
magnitude
Measure of the energy released during an earthquake
What causes earthquakes?
Sudden release of energy from rocks
elastic rebound theory
The sudden release of progressively stored strain in rocks results in movement along a fault.
Rayleigh waves
Type of surface waves that produces a "lazy rolling motion", like a rolling ocean
moment magnitude
a more precise measure of earthquake magnitude than the Richter scale, which is derived from the amount of displacement that occurs along a fault zone and estimates the energy released by an earthquake
Richter scale
a numerical scale for expressing the magnitude of an earthquake
a seismic gap is
a segment of a fault that has not experienced earthquakes for a long time
What are aftershocks?
a smaller earthquake following the main shock of a large earthquake.
aftershock
a smaller earthquake following the main shock of a large earthquake.
seismic waves
a wave of energy produced by an earthquake
Love waves
are most like S waves that have no vertical displacement
P waves are
compressional waves in which rock vibrates parallel to the direction of wave propagation
circumpacific belt
encircles the rim of the pacific ocean. Within this belt occurs approximately 80% of the worlds shallow focus quakes, 90% of the intermediate focus quakes, and nearly 100% of the deep focus quakes.
How can scientists forecast earthquakes
geological records
which of the following is NOT true of tsunamis
high wave height in deep water
elastic rebound theory
involves the sudden release of progressively stored strain in rocks, causing movement along a fault
earthquake
is the shaking and trembling that results from the movement of rock beneath Earth's surface
the Richter scale measures
magnitude of an earthquake
Benioff zones are found near
oceanic trenches
Seismogram
paper record of a seismic event
surface wave
seismic waves that travel along the Earth's surface
body wave (seismic wave)
seismic waves that travel through the Earth's interior spreading outward from the focus in all directions