three faults : LUSENET : Introductory Geology, Oswego State : One Thread

how do the three earthquake fault work?

-- Seul A lee (, October 04, 2004


Earthquakes create stress in rocks that may be manifested by surface faults. Faults are categorized according to the relative movement of the blocks on either side and by the force vectors responsible for the movement. Normal faults create a down-dropped block (graben). It is a response to stretching. We have normal faults all around the Adirondacks, a response to doming, and bordering the Hudson Highlands in northern New Jersey, a response to Triassic (and perhaps earlier) stretching. Schunemunk mountain is a graben bordered by normal faults. Reverse faults or thrust faults (lower angle than reverse) create upraised blocks (horsts). Thrust faults are common throughout the Appalachians and express the periodic plate collisons in this area. Slip-strike faults create lateral movement, described as right or left. The most famous fault of this kind in North America is the San Andreas, expressing the northwest movement of the Pacific plate (on which San Francisco rides)and the southeast movement of the North American plate (of which all but a coastal slice of California is part.)

-- peter matt (, October 08, 2004.

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