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III

Max Est. MMI

5 km WNW of Wauna, Washington

Magnitude3.9
Depth27.9 km
Time 2026-09-29T21:05:56.250000Z UTC: 2026-09-29T21:05:56.250000Z
USGS ID uw714111952
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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)
Wauna
WA
760 555
Burley
WA
760 373
Purdy
WA
760 464

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

Ground Shaking Intensities — Interpolated ShakeMap MMI

3 sites
Location MMI Description
Wauna
WA
Weak(III)
Burley
WA
Weak(III)
Purdy
WA
Weak(III)