Temporal and spatial heterogeneity of rupture process application in shakemaps of Yushu Ms7.1 earthquake, China

Abstract:

Studies have shown that estimates of ground motion parameter from ground motion attenuation relationship often greater than the observed value, mainly because multiple ruptures of the big earthquake reduce the source pulse height of source time function. In the absence of real-time data of the station after the earthquake, this paper attempts to make some constraints from the source, to improve the accuracy of shakemaps. Causative fault of Yushu Ms 7.1 earthquake is vertical approximately (dip 83 °), and source process in time and space was dispersive distinctly. Main shock of Yushu Ms7.1 earthquake can be divided into several sub-events based on source process of this earthquake. Magnitude of each sub-events depended on each area under the curve of source pulse of source time function, and location derived from source process of each sub-event. We use ShakeMap method with considering the site effect to generate shakeMap for each sub-event, respectively. Finally, ShakeMaps of mainshock can be aquired from superposition of shakemaps for all the sub-events in space. Shakemaps based on surface rupture of causative Fault from field survey can also be derived for mainshock with only one magnitude. We compare ShakeMaps of both the above methods with Intensity of investigation. Comparisons show that decomposition method of main shock more accurately reflect the shake of earthquake in near-field, but for far field the shake is controlled by the weakening influence of the source, the estimated Ⅵ area was smaller than the intensity of the actual investigation. Perhaps seismic intensity in far-field may be related to the increasing seismic duration for the two events. In general, decomposition method of main shock based on source process, considering shakemap of each sub-event, is feasible for disaster emergency response, decision-making and rapid Disaster Assessment after the earthquake.