Map Sheet 48 (2025 update) - MMI from PGV (2% in 50 years)

Description

The California Geological Survey (CGS) Map Sheet 48 (MS48) provides a depiction of expected ground shaking intensity from future earthquakes across the state. The shaking intensity is represented using the Modified Mercalli Intensity (MMI) scale, which describes the perceived earthquake shaking and correlates strongly with earthquake-induced damage. MS48 maps the level of shaking with a 2% probability of being exceeded in 50 years, equivalent to a 2,475-year average recurrence interval.
In addition to MS48, eight interactive MMI hazard maps are presented. These include MMIs calculated using alternative methods. For each method, MMIs at two different hazard levels were presented: one with a 2% probability of being exceeded in 50 years (equivalent to 2,475-year recurrence interval) and the other with 10% probability of being exceeded in 50 years (equivalent to 475-year recurrence interval). The Arc GIS interface allows users to select any two MMI hazard maps to compare side by side. MMI values were calculated using several ground motion to intensity conversion equations (GMICEs). See the “Scientific Background” on MS48 webpage for detailed information.
Due to software limitations, symbology cannot be added to this service. To match the symbology used in the MS48 MMI application, use the following configuration:
  • Number of Classes: 7
  • Classes & Hex Codes:
  • 4 - 5: #ffffbf
  • 5 - 6: #f5f500
  • 6 - 7: #f7ce00
  • 7 - 8: #fa7d00
  • 8 - 9: #fd2a00
  • 9 - 10: #c70808
  • 10 - 11: #8c0808

Resources

Name Format Description Link
ArcGIS Hub Dataset HTML Open resource
ArcGIS GeoService ArcGIS GeoServices REST API Open resource

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