Source parameters of moderate-to-large Chinese earthquakes from the time
evolution of P-wave peak displacement on strong motion recordings
Abstract
In this work we propose and apply a straightforward methodology for the
automatic characterization of the extended earthquake source, based on
the progressive measurement of the P-wave displacement amplitude at the
available stations deployed around the source. Specifically, we averaged
the P-wave peak displacement measurements among all the available
stations and corrected the observed amplitude for distance attenuation
effect to build the logarithm of amplitude vs. time function, named LPDT
curve. The curves have an exponential growth shape, with 31 an initial
increase and a final plateau level. By analyzing and modelling the LPDT
curves, the information about earthquake rupture process and earthquake
magnitude can be obtained. We applied this method to the Chinese strong
motion data from 2007-2015 with MS ranging between 4 and 8. We used a
refined model to reproduce the shape of the curves and different source
models based on magnitude to infer the source-related parameters for the
study dataset. Our study shows that the plateau level of LPDT curves has
a clear scaling with magnitude, with no saturation effect for large
events. By assuming a rupture velocity of 0.9Vs, we found a consistent
self-similar, constant stress drop scaling law for earthquakes in China
with stress drop mainly distributed between a lower level (0.23Mpa) and
a higher level (3.74Mpa). The derived relation between the magnitude and
rupture length can be used for probabilistic hazard analyses and
real-time applications of Earthquake Early Warning systems.