Earthquake Surface Slip-Length Data is Fit by Constant Stress Drop and is Useful for Seismic Hazard Analysis

Shaw, Bruce E.

We present a new method to use directly observable surface-slip measurements in seismic hazard estimates.We present measures of scaling-relation fits to slip length data. These fits show sublinear scaling, a slowing in the rate of slip increase for the longest ruptures, so that L scaling—scaling with the length of the rupture—does not hold out to very large aspect ratio events. We find the best fitting for a constant stress drop model, followed next by a square root of length model. The constant stress-drop model, newly introduced here, provides a geometrical explanation for a long-standing puzzle of why slip only begins to saturate at large aspect ratios. The good fit of the constant stress-drop model to the slip-length data lends further support to the observations of constant stress-drop scaling across the whole range of magnitudes of earthquakes, from small to great earthquakes. The good fit of the constant stress-drop model is also reflected by the low variability about the mean, with an average of less than a factor-of-2 variability in stress drop about the mean observed. Converting magnitude-area scaling into implied slip-length scaling, we determine qualitative consistency in the functional forms, but a quantitative difference of, on average, about 30 percent more slip estimated from magnitude area compared with slip length.


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Bulletin of the Seismological Society of America

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