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A Beginner's Guide to Retrieving Data from the SCEDC

Getting Event Information

The SCEDC hosts the catalog of events detected by the Southern California Seismic Network (SCSN). Started in 1932, this catalog is one of the oldest instrumental earthquake catalogs in the U.S. There are many ways to access the catalog. These tutorials show how to get information using the Catalog Search forms on this website.

  • Tutorial 1 shows you how to retrieve event summary information (origin time, location, magnitude).
  • Tutorial 2 shows you how to retrieve event parametric information (phase arrivals, moment tensors and focal mechanisms).
    • Those who have a background in seismological software, analysis and formats may want to refer to the Advanced Topics at the bottom of the page for programmatic access or use of specialized alternate catalogs.

    Tutorial 1: Retrieving Origin Time, Location, Magnitude Information From the SCSN Catalog

    We will be looking for information about the Jan 25, 2023 Mw 4.2 Malibu, CA earthquake. This event was felt throughout the L.A. Basin.

    • Step 1. Navigate to the Catalog Search forms.

      From the navigation bar at the top of any web page, click on "EQ Catalogs" and choose the "Catalog Search (1932-present)" item.

      You will see the Catalog Search forms. These forms allow you to search by several parameters, such as date, magnitude, geographical area, and more.

    • Step 2. Enter search parameters into the form.

      For this example, we will search by a date and magnitude range. Let's say we remembered it happened in January, 2023 and we knew its magnitude was over 4.

    • Step 3. View results.

      The results are shown below. We know now the time (in UTC), its latitude, longitude, and depth of the hypocenter. We can see other information such as how many station arrivals ("NPH") were used to determine the hypocenter and how many event based waveforms ("NGRM") are available for this event.

    Tutorial 2: Searching and Retrieving Event Parameteric Information From the SCSN Catalog

    Let's look at more details about the Jan 25, 2023 Mw 4.2 Malibu, CA earthquake.

    • Getting Phase Arrivals from the Catalog Search forms.

      The results in the previous tutorial show us that there are phase arrivals for this event. We can use the Catalog Search forms to retrieve them.

    • Navigate back to the Catalog Search form and choose the "Event ID" tab.
    • Use the eventid you retrieved from Tutorial 1 and "Output Format" = "Hypoinverse 2000".

    • The output is in Hypoinverse Phase format. It is meant as input into the HYPOINVERSE program. See Advanced Topics for more information on the Hypoinverse program.

    • Getting Focal Mechanisms from the Catalog Search forms.

      SCSN processing also produces focal mechanisms for events. We can use the Catalog Search forms to retrieve them.

    • Navigate back to the Catalog Search form and choose the "Focal Mechanisms" tab.
    • To retrieve the SCSN focal mechanism for the Malibu event, use the same search parameters used in Tutorial 1.

    • The search result will show the parameters of the mechanism.

    • Getting Moment Tensors from the Catalog Search forms.

      SCSN processing also produces moment tensors for events. We can use the Catalog Search forms to retrieve them. The process is very similar to retrieving focal mechanisms.

    • Navigate back to the Catalog Search form and choose the "Moment Tensors" tab.
    • To retrieve the SCSN moment tensor for the Malibu event, use the same search parameters used in Tutorial 1.

    • The search result will show the parameters of the mechanism.

    Look at our Getting Station Metadata and Getting Seismic Waveforms tutorials to see what additional data and information we can get about this event.

    Advanced Topics and References

    Division of Geological and Planetary Sciences | California Institute of Technology
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