Intensity Lab
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IV

Max Est. MMI

2 km W of Brawley, CA

Magnitude4.5
Depth15.9 km
Time 2026-05-10T03:39:29.810000Z UTC: 2026-05-10T03:39:29.810000Z
USGS ID ci41460512
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Ground Shaking Intensities — Interpolated ShakeMap MMI

3 sites
Location MMI Description
Brawley
CA 		Light(IV)
Imperial
CA 		Light(IV)
El Centro
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.

4 stations
Station MMI Description
Calipatria 2 (CI.CLI2) Light(IV)
Imperial (CI.IMP) Light(IV)
Westmorland (CE.11369) Light(IV)
Desert Research Extended Center (CI.DRE) Light(IV)

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
Imperial
CA 		760 227
El Centro
CA 		760 206

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 +0.26 0.54 0.59
BSSA14 +0.43 0.56 0.70
CY14 +0.33 0.51 0.61
CB14 +0.32 0.50 0.59
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)
Imperial (CI.IMP) 0.1287 Moderate(V) 3.767 Strong(VI)
Calipatria 2 (CI.CLI2) 0.0825 Moderate(V) 4.140 Strong(VI)
Westmorland (CE.11369) 0.0409 Light(IV) 3.333 Strong(VI)
Desert Research Extended Center (CI.DRE) 0.0223 Weak(III) 1.377 Moderate(V)
Schaffner Ranch (CI.SNR) 0.0215 Weak(III) 0.858 Light(IV)
Ocotillo Community Park (CI.OCP) 0.0210 Weak(III) 0.714 Light(IV)
Cook Ranch 2 (CI.COK2) 0.0163 Weak(III) 0.839 Light(IV)
Salton Sea Wildlife (SSW) (NP.5062) 0.0162 Weak(III) 0.794 Light(IV)
El Centro Array 1, Borchard Ranches (NP.5056) 0.0150 Weak(III) 0.606 Weak(III)
Elmore's Ranch (CI.ERR) 0.0138 Weak(II) 0.550 Weak(III)
El Centro (CI.ELO) 0.0114 Weak(II) 0.619 Weak(III)
Bonds Corner, Omlin Residence (NP.5054) 0.0091 Weak(II) 0.412 Weak(III)
Sam W. Stewart (CI.SWS) 0.0086 Weak(II) 0.312 Weak(III)
El Centro Array 11, McCabe School (NP.5058) 0.0082 Not felt(I) 0.567 Weak(III)
Niland (CE.11698) 0.0073 Not felt(I) 0.374 Weak(III)
Fire Station (NP.5491) 0.0072 Not felt(I) 0.278 Weak(III)
Coachella (CI.COA) 0.0072 Not felt(I) 0.262 Weak(II)
Fire Station (NP.5053) 0.0070 Not felt(I) 0.445 Weak(III)
Rock Hill (CI.RXH) 0.0055 Not felt(I) 0.357 Weak(III)
UABC Campus Mexicali (BC.UABX) 0.0051 Not felt(I) 0.311 Weak(III)
Salton City (CI.SAL) 0.0038 Not felt(I) 0.230 Weak(II)
Wister Waterfowl (CI.WWF) 0.0037 Not felt(I) 0.218 Weak(II)
Sweeney Pass (CI.SWP) 0.0036 Not felt(I) 0.111 Weak(II)
Carrizo (CI.CRR) 0.0034 Not felt(I) 0.163 Weak(II)
CERRO PRIETO (BC.CPX) 0.0033 Not felt(I) 0.149 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.