Max Est. MMI
9 km ESE of Willits, CA
Ground Shaking Intensities — Interpolated ShakeMap MMI
3 sites| Location | MMI |
|---|---|
|
Willits
CA |
IV |
|
Brooktrails
CA |
IV |
|
Redwood Valley
CA |
IV |
Seismic Station Observed MMI
MMI values are derived directly from observed ground motion measurements at seismic stations and are not spatially interpolated.
Engineering Ground Motion Parameters
GMPE predictions provide an independent check on the ShakeMap interpolated intensities above.
ShakeMap relies on seismic station recordings; in areas with sparse station coverage — or
for large teleseismic events and earthquakes outside dense West Coast networks — ShakeMap
MMI can be inaccurate. A significant difference between ShakeMap and GMPE estimates is a signal
that the ShakeMap result should be treated as preliminary.
Also includes site Vs30 values and raw ground motion parameters (PGA/PGV).
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Engineering Ground Motion Parameters
GMPE predictions provide an independent check on the ShakeMap interpolated intensities above. ShakeMap relies on seismic station recordings; in areas with sparse station coverage — or for large teleseismic events and earthquakes outside dense West Coast networks — ShakeMap MMI can be inaccurate. A significant difference between ShakeMap and GMPE estimates is a signal that the ShakeMap result should be treated as preliminary. Also includes site Vs30 values and raw ground motion parameters (PGA/PGV).
Site-Specific Vs30 Values
Shear-wave velocity in the upper 30 m, used for GMPE predictions.
| Location | Default Vs30 (m/s) | Site-Specific Vs30 (m/s) |
|---|---|---|
|
Willits
CA |
760 | 352 |
|
Brooktrails
CA |
760 | 468 |
|
Redwood Valley
CA |
760 | 369 |
MMI vs Distance — Default Vs30 (760 m/s)
All methods using the 760 m/s rock-site reference. ShakeMap values are independent of Vs30.
MMI vs Distance — Site-Specific Vs30
GMPEs use the site-specific Vs30 values shown in the table above. ShakeMap values are unchanged.
Peak Ground Motion Values — USGS ShakeMap
PGA and PGV interpolated from the USGS ShakeMap grid for this event. Values reflect ShakeMap's ground motion model, not GMPE estimates.
| Location | PGA (%g) | PGV (cm/s) |
|---|---|---|
|
Willits
CA |
2.9175 | 1.044 |
|
Brooktrails
CA |
1.7422 | 0.690 |
|
Redwood Valley
CA |
2.2030 | 0.778 |