Fast Moment Magnitude For Local Events Using Strong Motion Data

The seismicity of Romania is significantly affected by earthquakes produced by the Vrancea seismic source with intermediate depth events (3 shocks/century with magnitude Mw greater than 7.0). The seismic activity on the Romanian territory consists on both shallow and intermediate depth earthquakes. The crustal seismicity is moderate and more scattered in comparison with the intermediate depth one. The recent upgrade of the seismic network in Romania with high dynamic range accelerometers (114 real time seismic stations equipped with episensors) allows recording of moderate to large magnitude earthquakes at very close epicentral distances (less than 10-20 Km). A network for monitoring the strong motion that can occur in a given area records data that provide an excellent opportunity to study how source, path and site influence the ground motion, specifically that in the near-source area. Such data are essential for updating seismic hazard maps and consequently building codes and earthquake-resistant design. A fast seismic data analysis is essential to provide rapid and useful information to Authorities that have to take decisions immediately after a strong earthquake occurrence. Modern accelerometers are the only instruments that can provide near source high-quality data during a strong earthquake. The purpose of this work consists mainly in the estimation of moment magnitude Mw using the strong motion network of NIEP. A stable and automatic method developed by [1], has been implemented in real time data acquisition and processing system (ANTELOPE) to estimate in real time the seismic moment, the moment magnitude and the corner frequency of events recorded by accelerometers, using [2] method applied to S waves. The main goal is the independent estimation of seismic moment and corner frequency for all events recorded by the strong motion network.