Publications des scientifiques de l'IRD

Courboulex F., Vallée Martin, Causse M., Chounet A. (2016). Stress-drop variability of shallow earthquakes extracted from a global database of source time functions. Seismological Research Letters, 84 (4), p. 912-918. ISSN 0895-0695.

Titre du document
Stress-drop variability of shallow earthquakes extracted from a global database of source time functions
Année de publication
2016
Type de document
Article référencé dans le Web of Science WOS:000378490100014
Auteurs
Courboulex F., Vallée Martin, Causse M., Chounet A.
Source
Seismological Research Letters, 2016, 84 (4), p. 912-918 ISSN 0895-0695
We use the new global database of source time functions (STFs) and focal mechanisms proposed by Vallee (2013) using the automatic SCARDEC method (Vallee et al., 2011) to constrain earthquake rupture duration and variability. This database has the advantage of being very consistent since all the events with moment magnitudes M-w > 5.8 that have occurred during the last 20 years were reanalyzed with the same method and the same station configuration. We analyze 1754 shallow earthquakes (depth < 35 km) and use high-quality criteria for the STFs, which result in the selection of 660 events. Among these, 313 occurred on the subduction interface (SUB events) and 347 outside (NOT-SUB events). We obtain that for a given magnitude, STF duration is log normally distributed and that STFs are longer for SUB than NOT-SUB events. We then estimate the stress drop using a proxy for the rupture process duration obtained from the measurement of the maximum amplitude of the STF. The resulting stress drop is independent of magnitude and is about 2.5 times smaller for the subduction events compared with the other events. Assuming a constant rupture velocity and source model, the resulting standard deviation of the stress drop is 1.13 for the total dataset (natural log), and about 1 for separate datasets. These values are significantly lower than the ones generally obtained from corner-frequency analyses with global databases (similar to 1.5 for Allmann and Shearer, 2009) and are closer to the values inferred from strong-motion measurements (similar to 0.5 as reported by Cotton et al., 2013). This indicates that the epistemic variability is reduced by the use of STF properties, which allows us to better approach the natural variability of the source process, related to stress-drop variability and/or variation in the rupture velocity.
Plan de classement
Géophysique interne [066]
Localisation
Fonds IRD [F B010067646]
Identifiant IRD
fdi:010067646
Contact