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 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 to 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 0.9 Vs, we found a consistent self-similar, constant stress drop scaling law for earthquakes in China with stress drop mainly distributed at a lower level (0.2 MPa) and a higher level (3.7 MPa). The derived relation between the magnitude and rupture length may be feasible for real-time applications of Earthquake Early Warning systems.

Earthquake Source Parameters in Zagros Region (Iran) From the Time -Evolutive P-wave Displacement

“…In fact, Wang et al, [33] declared that this model is only able to correctly reproduce the rupture procedure of the events with Ms≤6.7, because of underestimated rupture length of the larger events in their dataset (Ms>6.7) in comparison with the other works of literature. To this end, they assumed that the corner-time (𝑇 𝑐 ) of the plateau level (𝑃 𝐿 ) corresponds to middle point of the average trapezoid plateau.…”

“…In principle, this network-based method assumes that rupture spreads radially on a circular fault at a constant velocity (𝑉 𝑟 ) with an isosceles triangular-shaped (Figure 2c) moment rate function, which seems sufficiently accurate to describe the source parameters of small-to-moderate events analyzed in previous articles [26][27]33]. Among these ones, Wang et al, [33] suggested that the rectangle fault (Haskell model) can be more suitable than the circular rupture model in the estimation of rupture length of the large events (Ms>6.7). Wang et.…”

“…Wang et. al., [33] analyzed 31 moderateto-large earthquakes that occurred from 2007 to 2015 in China with Ms ranging between 4 and 8.…”

Earthquake Seismic Moment, Rupture Radius and Stress-drop from P-wave Displacement Amplitude vs Time Curves

“…The original method to construct the LPDT curve required three main steps (see figure 1) : (1) the measurement of the logarithm of the maximum P-amplitude at all available stations within the same time window from the P-onset, (2) the correction of the amplitude for the distance attenuation (green curve in Figure 1a for an individual station) and (3) the average of all distance-corrected peak displacement values (green curve in Figure 1b for a given event) [13]- [15], [20].…”

“…To estimate the plateau and corner time of the LPDT curves, we model the curves with a 3-parameter, exponential function [20], [24]:…”