Intensity Lab
II

Max Est. MMI

10 km N of Lake Pillsbury, CA

Magnitude4.0
Depth10.6 km
Time 2026-10-28T12:01:11.470000Z UTC: 2026-10-28T12:01:11.470000Z
USGS ID nc75458907
ShakeMap View USGS ↗

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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Est. Vs30 Values

Estimated shear-wave velocity in the upper 30 m used in GMPE calculations. Ref. column shows the 760 m/s rock-site reference for comparison.

Location Ref. (760 m/s) Est. Vs30 (m/s)
Redwood Valley
CA 		760 369
Willits
CA 		760 352
Upper Lake
CA 		760 228

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 — default Vs30

MMI vs Distance — Est. Vs30

GMPEs use the Est. Vs30 values shown in the table above. ShakeMap values are independent of Vs30.

MMI vs distance — Est. Vs30

GMPE Residual — Observed − Predicted MMI

Signed residual at each seismic station. Positive values mean the GMPE underestimated shaking; negative values mean it overestimated. The dashed line at zero indicates perfect agreement.

GMPE residual plot

GMPE Predicted vs. Observed MMI at Seismic Stations

Each point is one seismic station. Points on the dashed 1:1 line indicate perfect agreement; above the line = GMPE underestimated shaking; below = overestimated.

GMPE predicted vs observed scatter

GMPE Performance — Station Observations

Statistics computed by comparing each GMPE's predicted MMI against ShakeMap observed MMI at seismic stations. Bias = mean(observed − predicted). Lower RMSE indicates better overall agreement with instrumental measurements.

GMPE Bias Sigma RMSE
ASK14 +0.09 0.31 0.32
BSSA14 +0.08 0.31 0.31
CY14 +0.08 0.30 0.31
CB14 +0.08 0.29 0.30
Bias > 0: GMPE underestimated shaking at stations. Bias < 0: GMPE overestimated shaking.

Peak Ground Motion — Seismic Station Observations

Recorded PGA and PGV at seismic stations, sorted by highest PGA. Top 25 stations shown. MMI (PGA) and MMI (PGV) are independent conversions via Worden et al. (2012) GMICE.

Station PGA (g) MMI (PGA) PGV (cm/s) MMI (PGV)
Hull Mountain (BK.HULL) 0.0073 Not felt(I) 0.299 Weak(III)
Van Arsdale (NC.GVA) 0.0051 Not felt(I) 0.238 Weak(II)
Bevans Ridge (BK.BEVN) 0.0044 Not felt(I) 0.196 Weak(II)
Barra Winery, Redwood Valley, CA (BK.BARR) 0.0020 Not felt(I) 0.242 Weak(II)
Navarro Ridge (NC.GNR) 0.0010 Not felt(I) 0.103 Weak(II)
Thermalito Afterbay Dam (WR.THER) 0.0009 Not felt(I) 0.008 Not felt(I)
Sherwood Rancheria area, Willits (BK.SHWD) 0.0008 Not felt(I) 0.032 Not felt(I)
Trough Springs/Crackerbox Ridge, CA 95979 (BK.GTSB) 0.0008 Not felt(I) 0.031 Not felt(I)
Orr Springs (BK.ORRS) 0.0007 Not felt(I) 0.034 Not felt(I)
Rackout Springs (NC.KRK) 0.0007 Not felt(I) 0.049 Not felt(I)
Cow Mountain (NC.GCWB) 0.0006 Not felt(I) 0.027 Not felt(I)
Spanish Ridge (NC.GSR) 0.0005 Not felt(I) 0.027 Not felt(I)
Etsel Ridge (BK.ETSL) 0.0004 Not felt(I) 0.056 Not felt(I)
Farley Peak (NC.KFP) 0.0004 Not felt(I) 0.020 Not felt(I)
Fire Station 27 (NP.1858) 0.0004 Not felt(I) 0.006 Not felt(I)
Spanish Creek (BK.SPAN) 0.0004 Not felt(I) 0.035 Not felt(I)
Black Butte Lake (NC.GBB) 0.0004 Not felt(I) 0.034 Not felt(I)
Hogback Ridge (NC.GHGB) 0.0004 Not felt(I) 0.027 Not felt(I)
Bradford Ranch, Boonville, CA (BK.BONV) 0.0004 Not felt(I) 0.024 Not felt(I)
Round Valley Indian Tribe, Mendocino County, CA (BK.RVIT) 0.0004 Not felt(I) 0.030 Not felt(I)
Wonder Ranch (NC.GWR) 0.0004 Not felt(I) 0.033 Not felt(I)
Clark Valley (BK.GCKB) 0.0003 Not felt(I) 0.025 Not felt(I)
Round Top Mountain (NC.GRT) 0.0003 Not felt(I) 0.030 Not felt(I)
Top of Konocti (NC.GTK) 0.0003 Not felt(I) 0.031 Not felt(I)
Montezuma Slough (WR.MOFF) 0.0002 Not felt(I) 0.090 Weak(II)
Source: USGS ShakeMap station recordings (view ShakeMap). PGA in g (fraction of gravitational acceleration); PGV in cm/s. The observed MMI shown on the map uses ShakeMap's reported instrumental intensity where available, or max(MMI from PGA, MMI from PGV) otherwise.

Ground Shaking Intensities — Interpolated ShakeMap MMI

3 sites
Location MMI Description
Redwood Valley
CA 		Weak(II)
Willits
CA 		Weak(II)
Upper Lake
CA 		Weak(II)

Seismic Station Observed MMI

MMI values are derived directly from observed ground motion measurements at seismic stations and are not spatially interpolated.

3 stations
Station MMI Description
Hull Mountain (BK.HULL) Weak(III)
Bevans Ridge (BK.BEVN) Weak(II)
Van Arsdale (NC.GVA) Weak(III)