Seismic Event Dossier•06:32 Local (22:32 UTC)(99y ago)

M 7.7 earthquake
Wuwei, Gansu, China

A magnitude 7.7 (MW) earthquake occurred on 1927-05-22, 06:32 local time (22:32 UTC) (99y ago), centered 32 km SW of Wuwei (China). The hypocenter was located at a shallow depth of 15 km. Primary telemetry verified by USGS.

Historical Landmark Earthquake

#24 of All Time

Curated Global Seismic Archive (1700–Present)

Top-100 Earthquakes

A magnitude 7.7 earthquake struck ⁨Wuwei, Gansu, China⁩ on 22 mai 1927. Documented deaths: 40,912.

Documented Fatalities40,912Source: NOAA NCEI Significant Earthquake Database

Fault KinematicsActive fault

Equivalent Energy5.35 Mt TNT

Magnitude

M 7.7

5.35 Mt TNT

Profondeur

15 km

shallow (Croûte superficielle)

Impact PAGER

red

> 1,000 fatalities

Blessés: > 5,000 · ~198.6M ressenti

Carte interactive de l'épicentre et des failles

37.67°N, 102.49°E

Faille21 km

Segment de faille active

Slip · ~15.0 mm/yr

Felt byMMI III+

~198.6M exposed

~18.5M strong shaking

Primary SolutionUSGS

USGS#iscgem909273reviewed

1 agencies reporting

Setting37.7°N

China

Continental / Inland crustal

Seismic Activity & Aftershock Sequence

Timeline of foreshocks, main rupture, aftershocks and machine learning risk probability evolution.

Hover or tap a point to inspect aftershocks and risk probability curve.

<35 km (superficiel)35–70 km (intermédiaire)>70 km (profond)Choc principal

Situation Monitoring

Continuous verification

Multi-agency verification of casualties, tsunami alerts, and seismic sequence

Key facts so far

Casualties

Damage assessment in progress

Tsunami Status

No tsunami threat

NOAA PTWC & regional buoys

Citizen Felt Reports

No felt reports submitted

Macroseismic DYFI verification

Aftershock Sequence

Monitoring

Aftershocks expected (Omori law)

LightGBM hazard model forecast

Multi-agency seismic telemetry active. Awaiting wire headlines.

Agency Discrepancy Matrix (Cross-Network Verification)

Comparing multi-network solutions from primary and teleseismic monitoring agencies.

Network / Source	Magnitude (Scale & Diff)	Depth & Diff	Epicenter & Shift (Δd)	Consensus	Event ID / Data
USGS United States Geological Survey · Global / US	M7.7(Mw)Ref	15.0 kmRef	37.67°, 102.49°Origin	Authoritative	iscgem909273

Why do agency magnitudes differ? Seismological agencies use different instrumentation networks, crustal velocity models, and mathematical magnitude scales (e.g. Moment Magnitude Mw vs Local Richter ML vs Surface Wave Ms). Differences of 0.1–0.3 are common and reflect physical observation geometry rather than errors.

Where it was felt

6 localités

Shaking intensity is modelled from magnitude, depth and distance (GMPE attenuation), not reported by residents.

Town	Distance	Intensity	Population
Wuwei · Gansu	32 km	MMI IX	493,092
Jinchang · Gansu	96 km	MMI VIII	144,363
Xining · Gansu	133 km	MMI VII	1,048,000
Lanzhou · Gansu	213 km	MMI VI	2,561,000
Zhangye · Gansu	227 km	MMI VI	230,728
Linxia · Gansu	238 km	MMI VI	534,555

Tectonic setting

Nearest mapped active fault: Segment de faille active, 21 km away, slip rate ~15.0 mm/yr (GEM Global Active Faults).

M 7.7 earthquake Wuwei, Gansu, China