Global variations of stress drop for moderate to large earthquakes

We investigate the global variation of earthquake stress drops using spectra of about 2000 events of m b ≥ 5.5 between 1990 and 2007. We use an iterative least squares method to isolate source displacement spectra from travel path and receiver contributions, based on a convolutional model. The observed P wave source spectra are corrected with a globally averaged empirical correction spectrum and estimates of near‐source attenuation. Assuming a Brune‐type source model, we estimate corner frequencies and compute stress drops. Stress drop estimates for individual earthquakes range from about 0.3 to 50 MPa, but the median stress drop of about 4 MPa does not vary with moment, implying earthquake self‐similarity…

• NS
  National Science Foundation
• SC
  Southern California Earthquake Center
• UG
  U.S. Geological Survey