What is an earthquake? A release of energy in Earth’s crust.
What are the main lessons Calif. learned from the 1989 Loma
Prieta and the 1994 Northridge quakes? Faults:
What is a fault? A plane (crack) that separates a body of rock in Earth’s crust ...across which there is significant displacement, the amount of which is called offset (m, cm), which is measured using markers (curbs, fences, etc.)
For a dipping fault, the hanging wall is the block positioned over the fault, the foot wall is under it.
Calif. contains all types of faults (strikeslip, normal, thrust/reverse, & oblique).
Are they all active?
What is a fault slip rate? distance(offset)/time(years)
What is a cumulative slip rate?
What is a fault trace? Where the fault plane meets the surface. How is that different than a fault plane?
If a fault does not break the surface, no fault trace is visible, and it is called a blind fault, which are important because the upper layers of rock fold over.
(Northridge 1994) San Andreas Fault (SAF):
What kind of fault is it? Right lateral, strikeslip
A restraining bend pushes together (mountains, thrust faults) while a releasing bend pulls apart (sag ponds/lakes, normal faults).
The segment names of SAF are: Earth’s Layers:
What are Earth’s chemical layers? (draw crust/mantle/core) What are Earth’s two mechanical layers? (draw lithosphere/asthenosphere)
What is a tectonic plate made of? Continental Drift and Seafloor Spreading:
Describe Wegener’s theory of continental drift: The hypothesis that the continents had once formed a single landmass before breaking apart and drifting to their present locations
A plausible driving force was missing. It did not help that Wegener was not a geologist. It is now accepted that the plates carrying the continents do move across the Earth's surface; ironically one of the chief outstanding questions is the one
Wegener failed to resolve: what is the nature of the forces propelling the plates?
Wegener noted the similarity of Mantovani's and his own maps of the former positions of the southern continents.
Through volcanic activity due to thermal expansion this continent broke and the new continents drifted away from each other because of further expansion of the ripzones, where the oceans now lie. This led Mantovani to propose an
Expanding Earth theory which has since been shown to be…