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Intensity Lab
III

Max Est. MMI

M4.3 earthquake · shaking intensity by town 20 km NNE of Indio, CA

Magnitude4.3
Depth3.7 km
Time 2026-01-21T08:30:07.650000Z UTC: 2026-01-21T08:30:07.650000Z
USGS ID ci41166223
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)
Sky Valley
CA 		760 352
Indio
CA 		760 228
Bermuda Dunes
CA 		760 294

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 +0.17 0.38 0.42
BSSA14 +0.13 0.36 0.38
CY14 +0.27 0.39 0.47
CB14 +0.21 0.37 0.43
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)
Keys View (CI.KYV) 0.0690 Moderate(V) 1.881 Light(IV)
Mirage (CI.MGE) 0.0249 Weak(III) 0.655 Weak(III)
Indio (CE.12904) 0.0222 Weak(III) 0.638 Weak(III)
Indio Hill (CI.IDO) 0.0192 Weak(III) 0.824 Weak(III)
Indio Quarry (CI.IDQ) 0.0119 Weak(III) 0.483 Weak(III)
Cathedral City (CE.12108) 0.0106 Weak(III) 0.219 Weak(II)
Thermal (CE.12541) 0.0105 Weak(III) 0.438 Weak(III)
La Quinta (CE.12951) 0.0099 Weak(III) 0.298 Weak(III)
Garner Valley (SB.GVDA) 0.0078 Weak(III) 0.215 Weak(II)
Polly Butte 2 (CI.POB2) 0.0073 Weak(III) 0.190 Weak(II)
Joshua Tree National Park Headquarters (CI.JTH) 0.0060 Weak(III) 0.333 Weak(III)
Idyllwild (CI.IDY) 0.0060 Weak(III) 0.101 Weak(II)
Thermal Canyon (CI.THM) 0.0057 Weak(II) 0.237 Weak(II)
Mission Creek (CI.MSC) 0.0054 Weak(II) 0.181 Weak(II)
Black Rock Canyon Campground 2 (CI.BLA2) 0.0054 Weak(II) 0.144 Weak(II)
Devers (CI.DEV) 0.0054 Weak(II) 0.241 Weak(II)
Keenwild Fire Station, Mountain Center, CA, USA (AZ.KNW) 0.0050 Weak(II) 0.069 Weak(II)
Cactus City (CI.CTC) 0.0049 Weak(II) 0.294 Weak(III)
Camp Scherman (CI.CSH) 0.0049 Weak(II) 0.087 Weak(II)
Skyland Ranch (CI.SLR) 0.0047 Weak(II) 0.135 Weak(II)
Sleepy Hollow (CI.SLH) 0.0043 Weak(II) 0.148 Weak(II)
Hemet 2 (CI.HMT2) 0.0042 Weak(II) 0.083 Weak(II)
Radec (CE.12092) 0.0039 Weak(II) 0.121 Weak(II)
Dunn Ranch (CI.DNR) 0.0039 Weak(II) 0.136 Weak(II)
Palm Springs Desert Museum (CI.PSD) 0.0036 Weak(II) 0.074 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
Sky Valley
CA 		Weak(III)
Indio
CA 		Weak(III)
Bermuda Dunes
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
Keys View (CI.KYV) Light(IV)
Indio Hill (CI.IDO) Weak(III)
Indio Quarry (CI.IDQ) Weak(III)