ISTI SeisComp Laboratory

istiMT: This module automatically computes a moment tensor for earthquakes of a certain magnitude (default is 7.5 Mw, but this is configurable). It uses pre-computed Green’s functions from the National Earthquake Information Center (NEIC) and can apply either the “WPhase” method or NEIC’s P-wave-based method for computing the focal mechanism. The main QuakeML focal mechanism message, along with the data and intermediary results, are saved in an HDF5 file.

istiAP: This module estimates rupture length and propagation using a sliding-window FK-analysis method. Like istiMT, it starts computation based on a magnitude threshold (default is 7.5). It finds a back-azimuth and apparent velocity for each window, then back-projects onto the original hypocenter to track rupture progression over time. Since the standard QuakeML message format doesn’t support this result, an “event” object is created to notify the user. Results are packaged in HDF5 format. Proper array configuration is necessary for meaningful results, as they depend on array geometry suitable for examining earthquakes at a teleseismic distance.

istiFFS: This module computes a finite fault solution by dividing the rupture area to provide detailed earthquake characteristics. It uses focal mechanism information for initial parameters and the same Green’s functions as istiMT. Since the results aren’t part of the QuakeML standard, users are notified via an “event” object, and the results are stored in an HDF5 file.

istiFFS: This module computes a finite fault solution by dividing the rupture area to provide detailed earthquake characteristics.

scevent: A function was added to find the nearest cities to an earthquake and report that information in the “event description.”. This function was modeled after an existing method that provided the region the earthquake is in and draws from the same table of information in which the regional description is located.

scautopick: Methods were added to roughly approximate pick polarity and wave first motion and pass that information along with the computed results.

scautoloc: ISTI modified the original association routine to handle user-defined picks outside the standard GUIs. This includes logic to “blacklist” picks from automatic locations and to force “dis-association” of picks from particular events. ISTI also added a QC method to filter out bad picks. While SeisComP provides QC methods using azimuthal gap, standard error, and other metrics, this change allows for a better solution by omitting up to three bad picks before re-submitting for a new location. The picks to be removed are identified through an “n squared” search over the set. This process, which can use significant system resources, can be turned on or off in the configuration.