GridMT: 4 Years of a Continuous Seismic Source Scanning in Northern California - Description, Performances, and Improvements

GridMT, a continuous realtime seismic waveform scanning algorithm, was launched in October 2012 by the Berkeley Seismological Laboratory to monitor the most seismically active region of California: the Mendocino region. Thanks to this tool, it becomes possible to automatically detect an event, estimate the seismic moment (and magnitude), and determine the focal mechanism of any moderate earthquakes located in a grid distributed over a region of interest. This operational scanning of a limited number of stations follows the approach proposed by Kawakatsu (1998) that is implemented in Japan since 2003. In order to correctly monitor the Mendocino region, two systems running in parallel are implemented to detect moderate earthquakes (M<7.5) and potentially tsunamigenic events on the Cascadia Subduction Zone (M>=8). We present a review of the milestones achieved during the first 4 years of the GridMT project as well as an analysis of the performances of the two running systems. Even though GridMT has shown some very remarkable results, progress can still be made. We show a series of steps that could be taken in order to improve the algorithm. After 4 years of continuous scanning GridMT reveals itself to be a great tool for seismic monitoring in Northern California and could be implemented in any other seismic region of interest.