Array-Based EEW

I am also interested in addressing the problems related to mitigating seismic and tsunami hazards through identifying diagnostic characteristics of early rupture processes of major earthquakes for establishing Earthquake Early Warning (EEW) systems. In Meng et al., BSSA, 2014, I proposed to develop an EEW (earthquake early warning) system composed of small-scale seismic arrays that track the rupture growth and directivity (doppler) effect. The system will provide a finite source estimation, which addresses the limitation of conventional EEW system using point source assumptions. We demonstrate the concept with the 2004 M 6.0 Parkfield earthquake and 2010 M7.2 Elmayor-Cucapah earthquake.

We explore the concept of characterizing rupture dimensions in real time for EEW using clusters of dense seismic arrays located near an active fault. Back tracing the waveforms of earthquake recorded by such arrays allows the estimation of the rupture size, duration and directivity in real-time, which enables the EEW of M > 7 earthquakes. The cartoon on the left demonstrates how such arrays track the propagation of an unilateral rupture along a vertical fault. Strong high-frequency (HF) seismic waves usually radiate from the rupture front. Tracking the source of the HF seismic waves during large earthquakes recovers the movement of the rupture front. The trajectory of the rupture front marks the fault extend involved in the earthquake.

The left figure demonstrate the idea of imaging seismic rupture with a small scale array. The color contours mark the rupture front with high slip velocity. The red and yellow “bang” symbols represent surface projections of the rupture front. The green triangles are the stations. The pink curve is the ray path of the incoming seismic waves. The dash lines mark the spatial extend of the rupture.