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Max Est. MMI

10 km ENE of Coso Junction, CA

Magnitude3.6
Depth2.6 km
Time 2026-08-23T09:16:58.730000Z UTC: 2026-08-23T09:16:58.730000Z
USGS ID ci41533752
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)
Inyokern
CA 		760 294
China Lake Acres
CA 		760 294
Searles Valley
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 +0.09 0.40 0.41
BSSA14 +0.08 0.36 0.37
CY14 +0.09 0.38 0.39
CB14 +0.07 0.31 0.32
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)
Coso Hot Springs 2 (CI.WCS2) 0.0406 Light(IV) 0.700 Light(IV)
Rose Valley 2 (CI.WRV2) 0.0347 Light(IV) 0.558 Weak(III)
Joshua Ridge: China Lake (CI.JRC2) 0.0194 Weak(III) 0.305 Weak(III)
Volcano Peak 2 (CI.WVP2) 0.0159 Weak(III) 0.342 Weak(III)
Mccloud Flat (CI.WMF) 0.0114 Weak(II) 0.498 Weak(III)
Haiwee, Pumping Plant (NP.1809) 0.0084 Weak(II) 0.269 Weak(II)
Bear Peak (CI.WBP) 0.0060 Not felt(I) 0.087 Weak(II)
Renegade Canyon (CI.WRC2) 0.0050 Not felt(I) 0.107 Weak(II)
Tower 2 (CI.TOW2) 0.0025 Not felt(I) 0.077 Weak(II)
Onyx Ranch (CI.WOR) 0.0019 Not felt(I) 0.038 Not felt(I)
Kern River P P #3 (CI.KRV3) 0.0016 Not felt(I) 0.018 Not felt(I)
Hanning Flat (CI.WHF) 0.0014 Not felt(I) 0.023 Not felt(I)
Porterville (CI.POR) 0.0011 Not felt(I) 0.012 Not felt(I)
Fish Rocks (CI.FSR) 0.0011 Not felt(I) 0.024 Not felt(I)
Snort (CI.SRT) 0.0009 Not felt(I) 0.030 Not felt(I)
Alta Sierra 2 (CI.WAS2) 0.0007 Not felt(I) 0.016 Not felt(I)
Darwin (CI.DAW) 0.0007 Not felt(I) 0.010 Not felt(I)
Vestal (CI.VES) 0.0007 Not felt(I) 0.015 Not felt(I)
Kern River P P #1 (CI.KRV1) 0.0006 Not felt(I) 0.008 Not felt(I)
Isabella (CI.ISA) 0.0005 Not felt(I) 0.015 Not felt(I)
Cottonwood Creek (CI.CWC) 0.0004 Not felt(I) 0.011 Not felt(I)
Siberia (CI.SRA) 0.0004 Not felt(I) 0.003 Not felt(I)
Little Horse 2 (CI.WLH2) 0.0004 Not felt(I) 0.010 Not felt(I)
China Lake (CI.CLC) 0.0004 Not felt(I) 0.005 Not felt(I)
Cattani Ranch (CI.TEH) 0.0003 Not felt(I) 0.008 Not felt(I)
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
Inyokern
CA 		Not felt(I)
China Lake Acres
CA 		Not felt(I)
Searles Valley
CA 		Not felt(I)

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
Mccloud Flat (CI.WMF) Weak(III)
Rose Valley 2 (CI.WRV2) Weak(III)
Coso Hot Springs 2 (CI.WCS2) Weak(III)