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Intensity Lab
II

Max Est. MMI

M3.6 earthquake · shaking intensity by town 3 km SW of Alamo, CA

Magnitude3.6
Depth13.0 km
Time 2026-06-07T15:37:48.620000Z UTC: 2026-06-07T15:37:48.620000Z
USGS ID nc75372426
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)
Alamo
CA 		760 352
Danville
CA 		760 335
Saranap
CA 		760 352

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 -0.25 0.40 0.47
BSSA14 -0.19 0.34 0.38
CY14 -0.31 0.41 0.52
CB14 -0.31 0.41 0.52
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)
Fire Station 2 (NP.1691) 0.0192 Weak(III) 0.627 Weak(III)
Lake Chabot (NC.CLCB) 0.0055 Weak(II) 0.164 Weak(II)
Round Hill Res (NC.CRH) 0.0051 Weak(II) 0.235 Weak(II)
Russellman Park (NC.CRPB) 0.0049 Weak(II) 0.140 Weak(II)
Pinole Ridge (NC.CPI) 0.0044 Weak(II) 0.130 Weak(II)
Summit Reservoir (NC.CSUM) 0.0041 Weak(II) 0.058 Weak(II)
Martinez Fire Station 14 (NP.1847B) 0.0036 Weak(II) 0.138 Weak(II)
Fire Station 31 (NP.1690) 0.0036 Weak(II) 0.134 Weak(II)
Mills College #2 (NC.CMC) 0.0035 Weak(II) 0.113 Weak(II)
San Pablo Ridge #2 (NC.CSPB) 0.0032 Weak(II) 0.037 Not felt(I)
Briones Reserve, Orinda, CA, USA (BK.BRIB) 0.0025 Weak(II) 0.106 Weak(II)
Cal Memorial Stadium, Berkeley, CA, USA (BK.CMSB) 0.0025 Weak(II) 0.048 Not felt(I)
Fire Station 1 (NP.1760) 0.0025 Weak(II) 0.087 Weak(II)
Morgan Territory (NC.CMOB) 0.0023 Weak(II) 0.085 Weak(II)
Bollinger Canyon Rd (NC.CBR) 0.0021 Weak(II) 0.063 Weak(II)
Fire Station 23 (NP.1855) 0.0021 Weak(II) 0.104 Weak(II)
San Leandro Hills (NC.CSL) 0.0020 Weak(II) 0.070 Weak(II)
Contra Costa FS 11 Clayton (NP.1846) 0.0019 Weak(II) 0.035 Not felt(I)
Fire Station 13 (NP.1857) 0.0019 Weak(II) 0.095 Weak(II)
Berkeley Country Club (NP.1737B) 0.0019 Weak(II) 0.029 Not felt(I)
Daly City FS 3 (NP.1804) 0.0018 Weak(II) 0.040 Not felt(I)
Grizzly Island (NC.NGI) 0.0017 Weak(II) 0.095 Weak(II)
FD Fire Training Center (NP.1861) 0.0017 Weak(II) 0.121 Weak(II)
Round Valley Regional Preserve (BK.RVRP) 0.0017 Weak(II) 0.047 Not felt(I)
LBL Building 88, Berkeley, CA, USA (BK.BL88) 0.0016 Weak(II) 0.069 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
Alamo
CA 		Weak(II)
Danville
CA 		Weak(II)
Saranap
CA 		Weak(III)

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
Bollinger Canyon Rd (NC.CBR) Weak(II)
Fire Station 31 (NP.1690) Weak(II)
Round Hill Res (NC.CRH) Weak(III)