Gisola

For real-time seismological and civil protection applications, such as tsunami wave generation warning, rapid strong motion determination, fault interaction, etc., it is essential to know, soon after a strong earthquake, the fault characteristics. This is accomplished by the automatic moment tensor determination procedure. Although such solutions are routinely applied in worldwide networks and large events, they are still challenging for regional applications starting with moderate-size earthquakes that still could be a threat.

Our solution to this problem is the Gisola open source software, a highly evolved moment tensor determination software tuned for regional networks and oriented toward high-performance computing. The program employs enhanced algorithms for waveform data selection and assessment via quality metrics, such as signal-to-noise ratio, waveform clipping, data and metadata inconsistency, long-period disturbances, and station evaluation based on power spectral density measurements, in parallel execution.

Gisola emerged from the ISOLated Asperities code, an extensively used manual moment tensor retrieval utility, and has been improved by exploiting the performance efficiency of multiprocessing on the CPU and GPU. Gisola offers the ability for a 4D spatiotemporal adjustable moment tensor grid search and multiple data resources interconnection to the International Federation of Digital Seismograph Networks Web Services (FDSNWS), the SeedLink protocol (a real-time data acquisition protocol and a client-server software), and the SeisComP Data Structure standard. The new software publishes its results in various seismological formats such as QuakeML and SC3ML, includes a website suite for MT solutions review, an e-mail notification system, and an integrated FDSNWS-event web service for MT solutions distribution. The operator has full control of all calculation aspects with an extensive and adjustable configuration.

Gisola has been extensively tested at the National Observatory of Athens with over 1000 MT calculations of regional earthquakes, and it is now the basic tool for moment tensor calculation in Greece. In a few minutes, a reliable solution for all events larger than ~Mw4Mw is computed, thus providing all the crucial information to the civil protection agencies to evaluate the related risk from this event. Gisola has been applied by seismic monitoring responsible agencies, in other parts of the world as well, for example, Colombia, Indonesia, and Albania, and we have received very good feedback.

The code is open source, it is available through GitHub (https://github.com/nikosT/Gisola), and besides the source code, a wiki page with extensive documentation is also available. Gisola is the product of collaboration between University of Patras (Prof. E. Sokos), the Geodynamics Institute of the National Observatory of Greece (Dr. C. Evangelidis, N. Triantafyllis, I. Fountoulakis) and the Department of Informatics, University of Piraeus, Piraeus, Greece (I. Venetis).