Data Services Newsletter

Volume 22 : No 2 : Summer 2020

Generalized GMVs: post-TA ground motion visualizations

Although the USArray Transportable Array (TA) is winding down its operations, the IRIS DMC will continue to produce and distribute its popular Ground Motion Visualization (GMV) data product that was originally designed based on the TA data. The GMVs that are produced on or after June 1, 2020, are created using a new visualization Python code that adds more flexibility to the GMV production by introducing the following advance features: utilization of all available open data from seismic stations across multiple FDSN Data Centers, enhanced graphics, use of mixed data channels, flexibility in viewport selection, use of “repeated” events to create Super GMVs, and capability to extend the GMV’s technological reach beyond the traditional seismic data. As before, the GMV product will continue to use the traditional US, North America, and Alaska viewports.

Figure 1 is a snapshot of a new vertical-component GMV generated for the January 28, 2020 magnitude 7.7 Cuba Region earthquake. This GMV (click on Figure 1 to play) was created using all openly available LHZ, BHZ or HHZ channel data that satisfied the GMV production QC criteria (see the GMV data product page). This GMV (Figure 1), in comparison to the one produced by the legacy GMV code (Figure 2), provides an improved station coverage in the western US and Canada. If needed, the flexibility in the viewport selection and access to a larger pool of stations allow visualization of the ground motion due to this earthquake at global (Figure 3) and European (Figure 4) scales.

New GMV
Figure 1. An enhanced vertical-component GMV for the January 28, 2020 magnitude 7.7 Cuba Region earthquake. For each station the requested channel is either LHZ, BHZ or HHZ. Only stations that were available at the time of request and passed the QC criteria of the script are included. The trace is the vertical seismogram from a reference station with its location marked by a down-pointing green triangle ▼ on the map. The event location is marked by a yellow star. The vertical red line | on the trace indicates the time corresponding the displayed GMV frame (Click on image to play).

Old GMV
Figure 2. A traditional vertical-component GMV for the January 28, 2020 magnitude 7.7 Cuba Region earthquake. Stations are those available through DMC(_REALTIME virtual network) that have LHZ channel data. The trace is the vertical seismogram from a reference station with its location marked by a green circle ◯ on the map. The vertical red line | on the trace indicates the time corresponding the displayed GMV frame (Click on image to play).

Global
Figure 3. A vertical-component GMV for the January 28, 2020 magnitude 7.7 Cuba Region earthquake with a global view. For each station the requested band is either LH or BH. Only stations that were available at the time of request and passed the QC criteria of the script are included. The trace is the vertical seismogram from a reference station with its location marked by a down-pointing green triangle ▼ on the map. The event location is marked by a yellow star. The vertical red line | on the trace indicates the time corresponding the displayed GMV frame (Click on image to play).

Europe
Figure 4. A vertical-component GMV for the January 28, 2020 magnitude 7.7 Cuba Region earthquake with the GMV pointed to Europe. For each station the requested band is either LH or BH. Only stations that were available at the time of request and passed the QC criteria of the script are included. The trace is the vertical seismogram from a reference station with its location marked by a down-pointing green triangle ▼ on the map. The vertical red line | on the trace indicates the time corresponding the displayed GMV frame (Click on image to play).

by Manoch Bahavar (IRIS Data Management Center)

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