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Stress Drop and Source Scaling of Recent Earthquake Sequences across the United States

Qimin Wu, & Martin C. Chapman

Published August 15, 2016, SCEC Contribution #6924, 2016 SCEC Annual Meeting Poster #241

Knowledge of source scaling and variation in stress drop are essential to a better understanding of source physics and strong ground-motion prediction. Due to the large uncertainties in stress drop measurements, many previous studies have found results showing both self-similar and non-self-similar scaling relationships between large and small earthquakes. Moreover, the validity of the recently proposed idea that induced earthquakes in the central US have low stress drops needs to be tested in a reliable and systematic way.

We investigate the stress drop and source scaling of four recent earthquake sequences across the US: the 2011 Mw 5.7 Mineral, Virginia earthquake, the 2011 Mw 5.6 Prague, Oklahoma earthquake, the 2014 Mw 6.0 South Napa, California earthquake and the 2016 Mw 5.1 Fairview, Oklahoma earthquake. We apply the coda spectral ratio method, which enables us to separate the source effect from the path propagation and site response effects, to obtain reliable estimates of corner frequencies and stress drops. We demonstrate that the use of the coda spectral ratio method can produce more stable estimates than the use of the direct S-waves in the conventional empirical Green’s function (EGF) or spectral ratio method. We carefully examine the decay of coda envelopes between selected event pairs, and the corner frequencies and stress drops are estimated by modeling the observed source spectral ratio with the omega-squared source spectral model. Our results shed light on the yet un-resolved question whether potentially induced earthquakes are different from tectonic earthquakes in terms of stress drop and source scaling across the US.

Key Words
Source Parameters, Stress Drop, Coda Spectral Ratio

Wu, Q., & Chapman, M. C. (2016, 08). Stress Drop and Source Scaling of Recent Earthquake Sequences across the United States. Poster Presentation at 2016 SCEC Annual Meeting.

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