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II

Max Est. MMI

28 km SSW of Alamo, Nevada

Magnitude3.7
Depth6.6 km
Time 2026-04-30T07:44:58.887000Z UTC: 2026-04-30T07:44:58.887000Z
USGS ID nn00916840
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Ground Shaking Intensities — Interpolated ShakeMap MMI

3 sites
Location MMI
Alamo
NV
II
Moapa Town
NV
I
Caliente
NV
I

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
Pahroc Range, Nevada. (GPS 12/04/2000) w84 (NN.PRN) I
Sheep Range, Nevada w84gm (NN.SHP) I
Pioche, NV, USA - NN reactivation (NN.PIO) I

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)
Alamo
NV
760 296
Moapa Town
NV
760 374
Caliente
NV
760 560

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 +0.00 0.00 0.00
BSSA14 +0.00 0.00 0.00
CY14 +0.00 0.00 0.00
CB14 +0.00 0.00 0.00
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)
Pahroc Range, Nevada. (GPS 12/04/2000) w84 (NN.PRN) 0.0005 I 0.015 I
Iron County Adult Education (UU.IAE) 0.0005 I 0.007 I
Sheep Range, Nevada w84gm (NN.SHP) 0.0003 I 0.002 I
Santa Clara, Utah (UU.SCUT) 0.0002 I 0.015 I
FORGE 1 (UU.FOR1) 0.0002 I 0.002 I
Washington County School District (UU.WDO) 0.0001 I 0.005 I
Veyo Road, UT (UU.VRUT) 0.0001 I 0.006 I
Pioche, NV, USA - NN reactivation (NN.PIO) 0.0001 I 0.006 I
Little Creek Mountain, UT (UU.LCMT) 0.0000 I 0.001 I
Zion National Park, UT (UU.ZNPU) 0.0000 I 0.003 I
Willow Creek Ranch, Ely, NV, USA - NN reactivation (NN.Q12A) 0.0000 I 0.002 I
FORGE 7 (UU.FOR7) 0.0000 I 0.001 I
FORGE 5 (UU.FOR5) 0.0000 I 0.001 I
FORGE 8 (UU.FOR8) 0.0000 I 0.001 I
FORGE 6 (UU.FOR6) 0.0000 I 0.001 I
FORU - Temp Station (UU.FORU) 0.0000 I 0.001 I
Shurtz Canyon (UU.SZCU) 0.0000 I 0.001 I
Pine Springs, UT (UU.PSUT) 0.0000 I 0.001 I
FOR2 (UU.FOR2) 0.0000 I 0.001 I
Troy Canyon, Currant, NV, USA (NN.R11B) 0.0000 I 0.001 I
Cedar City (UU.CCUT) 0.0000 I 0.001 I
Kanab, Coral Pink Sand Dunes State Park (UU.KNB) 0.0000 I 0.001 I
Hualapai Mountain Park, Kingman, AZ, USA (AE.W13A) 0.0000 I 0.001 I
Tonopah, Nevada, USA (LB.TPH) 0.0000 I
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.