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IV

Max Est. MMI

2 km ESE of Frazier Park, CA

Magnitude4.4
Depth13.1 km
Time 2026-07-12T10:38:04.720000Z UTC: 2026-07-12T10:38:04.720000Z
USGS ID ci41291863
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Ground Shaking Intensities — Interpolated ShakeMap MMI

3 sites
Location MMI Description
Lebec
CA
Light(IV)
Frazier Park
CA
Weak(III)
Pine Mountain Club
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.

5 stations
Station MMI Description
Hungry Valley SVR State Park (CI.HRV) Light(IV)
Bailey (CI.BAI) Light(IV)
Castaic Valley West (CI.CVW) Light(IV)
Lone Juniper Ranch (CI.LJR) Light(IV)
Tehachapi (CI.THC) 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)
Lebec
CA
760 374
Frazier Park
CA
760 352
Pine Mountain Club
CA
760 711

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 +0.37 0.52 0.64
BSSA14 +0.41 0.57 0.70
CY14 +0.38 0.52 0.64
CB14 +0.37 0.51 0.63
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)
Hungry Valley SVR State Park (CI.HRV) 0.1086 Moderate(V) 3.644 Strong(VI)
Castaic Valley West (CI.CVW) 0.0487 Light(IV) 1.682 Moderate(V)
Bailey (CI.BAI) 0.0484 Light(IV) 1.802 Moderate(V)
Lakeview (CE.35511) 0.0386 Light(IV) 0.851 Light(IV)
Frazier Mountain (CI.FRM) 0.0325 Light(IV) 0.906 Light(IV)
Tehachapi (CI.THC) 0.0318 Light(IV) 1.131 Light(IV)
Lone Juniper Ranch (CI.LJR) 0.0269 Light(IV) 1.274 Light(IV)
Tejon Ranch (CI.TJR) 0.0253 Weak(III) 0.762 Light(IV)
Lockwood Valley Maintenance Yard (CI.LMY) 0.0248 Weak(III) 0.627 Weak(III)
Mount Pinos (CI.MPI) 0.0165 Weak(III) 0.454 Weak(III)
Arvin (CI.ARV) 0.0159 Weak(III) 0.424 Weak(III)
High Desert Hunt Club (CI.HDH) 0.0153 Weak(III) 0.452 Weak(III)
Mount Abel (CI.ABL) 0.0127 Weak(II) 0.279 Weak(III)
Burnt Peak (CI.BTP) 0.0122 Weak(II) 0.423 Weak(III)
Frazier Park (CE.25657) 0.0093 Weak(II) 0.330 Weak(III)
Calstate Bakersfield (CI.BAK) 0.0088 Weak(II) 0.249 Weak(II)
El Tejon (CI.TEJ) 0.0077 Not felt(I) 0.158 Weak(II)
Kern River P P #1 (CI.KRV1) 0.0065 Not felt(I) 0.105 Weak(II)
Choke Cherry (CI.CRY) 0.0064 Not felt(I) 0.300 Weak(III)
Antelope Valley Poppy Reserve (CI.POP) 0.0053 Not felt(I) 0.226 Weak(II)
South Mountain (CI.SMT) 0.0044 Not felt(I) 0.261 Weak(II)
Leona Valley (CI.LEO) 0.0042 Not felt(I) 0.134 Weak(II)
Neenach (CI.NEN) 0.0038 Not felt(I) 0.187 Weak(II)
Porterville (CI.POR) 0.0037 Not felt(I) 0.052 Not felt(I)
Cattani Ranch (CI.TEH) 0.0034 Not felt(I) 0.084 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.