Earthquake Centroid Locations Using Calibration from Ambient Seismic Noise

Zhongwen Zhan, Shengji Wei, Sidao Ni, & Donald V. Helmberger

Published 2011, SCEC Contribution #1624

Earthquakes occur in complex geology and prove difficult to locate because of uncertainties in the seismic models. Essentially, solving for both source location and 3D structure simultaneously depends on the starting model and source distribution of past events. Regional earthquakes at ranges from 100 km to 300 km normally produce stable surface waves at period 10-100s. If the travel times or lags of the phases due to the path effect are known relative to a reference model, we can locate events without knowledge of past events. Here, we use ambient seismic noise for such a calibration. We cross-correlate the seismic stations near the earthquake with stations 100-300 km away to obtain the 10-100s surface wave Green’s functions. Then the travel times of these surface waves are measured relative to the reference model. The new method is tested in southern California to locate the 2008 Chino Hills earthquake and seismic stations not used in the calibration. A distribution of 5-10 stations with azimuthal gaps less than 120 degrees is sufficient to locate events within a few kilometers.

Zhan, Z., Wei, S., Ni, S., & Helmberger, D. V. (2011). Earthquake Centroid Locations Using Calibration from Ambient Seismic Noise. Bulletin of the Seismological Society of America,.