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Source Parameters Estimation Of Reservoir-Induced Earthquakes In Northeastern Brazil Using Empirical Green´s Function Analysis
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, II Simpósio Brasileiro de Geofísica, Sep 2006, cp-198-00044
Abstract
In the Açu dam area (NE Brazil), a digital seismograph local network was deployed for nearly three years and recorded one of the best examples of Reservoir-induced seismicity on a near-homogeneous Precambrian crystalline basement. The hypocentral error location are approximately 100m and are very suitable for investigating a possible relationship between pore-pressure diffusion and source parameters like stress drop, rupture velocity, source duration and rupture length. In order to obtain these source parameters from recorded seismograms, attenuation and site effects have to be removed. Empirical Green´s Functions (EGF) is an alternative way to extract the earthquake source information from the recorded digital seismograms. Here we present results from EGF analysis of 6 earthquakes in the Açu dam area. Estimates of source duration and corner frequency imply low stress drop (10 to 100 MPa) for these shallow reservoir-induced seismicity events. These are similar to tectonic earthquakes, suggesting that hypocentral depths and the presence of water do not affect stress drop.