(NAS Colloquium) Earthquake Prediction The Scientific Challenge (1996) / Chapter Skim
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The repetition of large-earthquake ruptures
The repetition of large-earthquake ruptures
Pages 3764-3771
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From page 3764... ...
, they conclude that geometrical irregularities along faults and the spectrum of fault sizes in a region are what produce G-R distributions, but that simple, individual faults ought to pro duce highly regular repetition of similar events. The concept of a "characteristic earthquake," in which the failure of one fault or one portion of a fault occurs repeatedly in events with nearly identical rupture lengths, locations, and slip magnitudes, arose more than a decade ago, from paleo seismic studies along the San Andreas and Wasatch faults (4, 5~.
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From page 3765... ...
Along both the Lost River Range fault and Superstition Hills fault, the basic slip functions have been repeating. Interevent deviations at any one site are almost always less than an order of magnitude and most commonly less than a factor of two.
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From page 3766... ...
This ,= 4 locality provides evidence both for characteristic slip and for leaky ° patch boundaries. Principal source of the 1983 earthquake was the C, Thousand Springs segment of the Lost River Range fault, but minor, ~ 3 discontinuous rupture also occurred on parts of the Warm Spring A, segment.
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From page 3767... ...
Paleoseismic data support the general aspects of such a model. If offsets as small as the 1940 and 1979 values are typical along the northern 20 km of the fault, then the average time between such events must be very short, because the long-term slip rate of the fault must be close to the sum of the slip rates of the San Jacinto and San Andreas fault zones, which feed, at least in part, into the Imperial fault from the north.
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From page 3768... ...
More evidence for leakage across patch boundaries comes from two other historical and prehistorical ruptures: The Lost River Range fault and the faults of the Landers earthquake. One part of the 1983 rupture of the Lost River Range fault, not mentioned above, exhibits noncharacteristic behavior that may be evidence of a leaky patch boundary.
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From page 3769... ...
These low-slip segments of the Emerson and the Camp Rock faults are nearly devoid of aftershocks, and inversions of both geodetic and seismographic data indicate that the slip did not extend more than a kilometer or so below the surface traces (21, 22, 29-314. A reasonable explanation for the shallowness of slip and paucity of aftershocks is that this portion of the rupture was driven by static stresses induced by that portion of the Emerson fault farther south that experienced 3 m or more of dextral slip.
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From page 3770... ...
The Thousand Springs segment of the Lost River Range fault experiences dip-slip offsets of up to a couple of meters. If slip on the central patch of the Imperial fault is similar from event to event, then the 1940 values of 5-6 m would be characteristic, as they are along the San Andreas fault.
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From page 3771... ...
Well-documented examples of repeated fault rupture are rare. But sparse available data support the view that smooth, individual fault patches fail during characteristic slip events.
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