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Intensity Lab
IV

Max Est. MMI

M4.4 earthquake · shaking intensity by town 3 km WSW of Brawley, CA

Magnitude4.4
Depth15.1 km
Time 2026-05-10T02:22:08.170000Z UTC: 2026-05-10T02:22:08.170000Z
USGS ID ci41460112
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)
Brawley
CA 		760 227
Westmorland
CA 		760 211
Imperial
CA 		760 227

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 -0.31 0.43 0.53
BSSA14 -0.11 0.35 0.37
CY14 -0.27 0.43 0.50
CB14 -0.31 0.45 0.55
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)
Airport Hangar (NP.5060) 0.6027 Severe(VIII) 14.010 Strong(VI)
Imperial (CI.IMP) 0.1202 Strong(VI) 2.854 Light(IV)
Westmorland (CE.11369) 0.0774 Moderate(V) 2.535 Light(IV)
Calipatria 2 (CI.CLI2) 0.0665 Moderate(V) 3.052 Light(IV)
Desert Research Extended Center (CI.DRE) 0.0308 Light(IV) 0.965 Weak(III)
El Centro Array 1, Borchard Ranches (NP.5056) 0.0232 Weak(III) 0.633 Weak(III)
Schaffner Ranch (CI.SNR) 0.0227 Weak(III) 0.857 Weak(III)
Salton Sea Wildlife (SSW) (NP.5062) 0.0172 Weak(III) 0.659 Weak(III)
Cook Ranch 2 (CI.COK2) 0.0117 Weak(III) 0.432 Weak(III)
Bonds Corner, Omlin Residence (NP.5054) 0.0096 Weak(III) 0.358 Weak(III)
Ocotillo Community Park (CI.OCP) 0.0095 Weak(III) 0.320 Weak(III)
Elmore's Ranch (CI.ERR) 0.0088 Weak(III) 0.302 Weak(III)
El Centro (CI.ELO) 0.0070 Weak(III) 0.240 Weak(II)
Rock Hill (CI.RXH) 0.0062 Weak(III) 0.185 Weak(II)
CA:El Centro;ECA11 McCabe Sch (NP.5058) 0.0059 Weak(III) 0.238 Weak(II)
Wister Waterfowl (CI.WWF) 0.0056 Weak(II) 0.158 Weak(II)
Sam W. Stewart (CI.SWS) 0.0056 Weak(II) 0.163 Weak(II)
Coachella (CI.COA) 0.0050 Weak(II) 0.199 Weak(II)
Ruthven (CI.RUN) 0.0042 Weak(II) 0.126 Weak(II)
Yuha Desert (CI.YUH2) 0.0042 Weak(II) 0.052 Not felt(I)
CA:Pine Valley;FS (NP.5491) 0.0040 Weak(II) 0.135 Weak(II)
Campo Elementary School (CI.CPO) 0.0038 Weak(II) 0.077 Weak(II)
UABC Campus Mexicali (BC.UABX) 0.0037 Weak(II) 0.155 Weak(II)
Fire Station (NP.5053) 0.0037 Weak(II) 0.171 Weak(II)
CERRO PRIETO (BC.CPX) 0.0028 Weak(II) 0.103 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
Brawley
CA 		Light(IV)
Westmorland
CA 		Light(IV)
Imperial
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.

4 stations
Station MMI Description
Airport Hangar (NP.5060) Strong(VI)
Calipatria 2 (CI.CLI2) Light(IV)
Imperial (CI.IMP) Light(IV)
Westmorland (CE.11369) Light(IV)