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IV

Max Est. MMI

4 km N of San Leandro, CA

Magnitude4.1
Depth5.2 km
Time 2026-08-13T15:30:04.660000Z UTC: 2026-08-13T15:30:04.660000Z
USGS ID nc75417557
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)
San Leandro
CA
760 293
Ashland
CA
760 293
Castro Valley
CA
760 408

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 +0.39 0.60 0.72
BSSA14 +0.40 0.59 0.71
CY14 +0.41 0.60 0.72
CB14 +0.40 0.59 0.71
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)
Lake Chabot (NC.CLCB) 0.0638 Light(IV) 1.788 Moderate(V)
San Leandro Hills (NC.CSL) 0.0618 Light(IV) 3.128 Strong(VI)
Fire Station 13 (NP.1857) 0.0345 Light(IV) 1.357 Light(IV)
Fire Station 27 (NP.1858) 0.0343 Light(IV) 1.750 Moderate(V)
Fire Station 20 (NP.1859) 0.0324 Light(IV) 1.126 Light(IV)
Fire Station 4 (NP.1756) 0.0284 Light(IV) 1.417 Moderate(V)
Fire Station 23 (NP.1855) 0.0212 Weak(III) 1.252 Light(IV)
San Ramon (NC.CSR) 0.0187 Weak(III) 0.851 Light(IV)
Mills College (NC.CMC) 0.0175 Weak(III) 0.639 Weak(III)
San Leandro FS 11 (NP.1836) 0.0168 Weak(III) 0.795 Light(IV)
FD Fire Training Center (NP.1861) 0.0115 Weak(II) 0.711 Light(IV)
Fire Station 31 (NP.1690) 0.0087 Weak(II) 0.816 Light(IV)
Union City FS 2 Alvarado Bl (NP.1802) 0.0087 Weak(II) 0.371 Weak(III)
Round Hill Res (NC.CRH) 0.0086 Weak(II) 0.509 Weak(III)
Garin Park (surface) (NC.CGP) 0.0083 Not felt(I) 0.446 Weak(III)
Fire Station 16 (NP.1689) 0.0080 Not felt(I) 0.375 Weak(III)
Niles Canyon (NC.CNI) 0.0077 Not felt(I) 0.309 Weak(III)
Vallecitos (NC.CVL) 0.0077 Not felt(I) 0.399 Weak(III)
Cal Memorial Stadium, Berkeley, CA, USA (BK.CMSB) 0.0066 Not felt(I) 0.237 Weak(II)
LBL Building 67, Berkeley, CA, USA (BK.BL67) 0.0065 Not felt(I) 0.302 Weak(III)
Brushy Peak (NC.CBP) 0.0064 Not felt(I) 0.316 Weak(III)
LBL Building 88, Berkeley, CA, USA (BK.BL88) 0.0059 Not felt(I) 0.272 Weak(II)
Round Valley Regional Preserve (BK.RVRP) 0.0054 Not felt(I) 0.193 Weak(II)
Russellman Park (NC.CRPB) 0.0049 Not felt(I) 0.183 Weak(II)
Forest Fire Station (NP.1688) 0.0047 Not felt(I) 0.155 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
San Leandro
CA
Light(IV)
Ashland
CA
Light(IV)
Castro Valley
CA
Light(IV)

Seismic Station Observed MMI

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

7 stations
Station MMI Description
San Leandro Hills (NC.CSL) Light(IV)
Lake Chabot (NC.CLCB) Light(IV)
Fire Station 27 (NP.1858) Light(IV)
Fire Station 4 (NP.1756) Light(IV)
Fire Station 23 (NP.1855) Light(IV)
Fire Station 13 (NP.1857) Light(IV)
Fire Station 20 (NP.1859) Light(IV)