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Intensity Lab
IV

Max Est. MMI

M4.0 earthquake · shaking intensity by town 3 km WSW of Brawley, CA

Magnitude4.0
Depth9.2 km
Time 2026-05-10T03:13:23.720000Z UTC: 2026-05-10T03:13:23.720000Z
USGS ID ci41460416
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 -0.19 0.36 0.41
BSSA14 -0.13 0.30 0.33
CY14 -0.15 0.32 0.36
CB14 -0.13 0.31 0.34
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) 0.2383 Very Strong(VII) 4.766 Moderate(V)
Imperial (CI.IMP) 0.0345 Light(IV) 0.651 Weak(III)
Naval Air Facility El Centro (NP.5051) 0.0281 Light(IV) 0.508 Weak(III)
Calipatria 2 (CI.CLI2) 0.0149 Weak(III) 0.457 Weak(III)
El Centro Array 5, James Rd (NP.952) 0.0133 Weak(III) 0.431 Weak(III)
El Centro Array 1, Borchard Ranches (NP.5056) 0.0072 Weak(III) 0.141 Weak(II)
Schaffner Ranch (CI.SNR) 0.0050 Weak(II) 0.249 Weak(II)
Salton Sea Wildlife (SSW) (NP.5062) 0.0049 Weak(II) 0.134 Weak(II)
Cook Ranch 2 (CI.COK2) 0.0043 Weak(II) 0.217 Weak(II)
Bonds Corner, Omlin Residence (NP.5054) 0.0041 Weak(II) 0.127 Weak(II)
El Centro (CI.ELO) 0.0036 Weak(II) 0.128 Weak(II)
Ocotillo Community Park (CI.OCP) 0.0029 Weak(II) 0.085 Weak(II)
Wister Waterfowl (CI.WWF) 0.0027 Weak(II) 0.067 Weak(II)
Coachella (CI.COA) 0.0021 Weak(II) 0.097 Weak(II)
Rock Hill (CI.RXH) 0.0020 Weak(II) 0.052 Not felt(I)
CA:El Centro;ECA11 McCabe Sch (NP.5058) 0.0020 Weak(II) 0.090 Weak(II)
Elmore's Ranch (CI.ERR) 0.0017 Weak(II) 0.085 Weak(II)
UABC Campus Mexicali (BC.UABX) 0.0017 Weak(II) 0.050 Not felt(I)
Sam W. Stewart (CI.SWS) 0.0016 Weak(II) 0.046 Not felt(I)
East Mesa (CI.EMS) 0.0015 Weak(II) 0.043 Not felt(I)
Fire Station (NP.5053) 0.0014 Weak(II) 0.051 Not felt(I)
Yuha Desert (CI.YUH2) 0.0013 Weak(II) 0.014 Not felt(I)
Ejido Yucatan (BC.YUC2X) 0.0013 Not felt(I) 0.057 Weak(II)
CERRO PRIETO (BC.CPX) 0.0011 Not felt(I) 0.036 Not felt(I)
Pescaderos la 14 (BC.PESCX) 0.0010 Not felt(I) 0.059 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 		Weak(III)
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.

3 stations
Station MMI Description
Airport Hangar (NP.5060) Moderate(V)
Imperial (CI.IMP) Weak(III)
Naval Air Facility El Centro (NP.5051) Weak(III)