HISTORICAL TSUNAMI RECORDNovember 1, 1755

Major Ocean Tsunami Generated (Historical Record)

This undersea earthquake generated recorded tsunami waves across coastal and trans-oceanic sectors. Preserved in seismic archive for scientific reference — no active hazard exists.

Seismic Event Dossier•08:40 Local (09:40 UTC)(proprio ora)

Earthquake near
North Atlantic Ocean (Portugal)

A magnitude 8.5 (MW) earthquake occurred on 1755-11-01, 08:40 local time (09:40 UTC) (proprio ora), centered North Atlantic Ocean (254 km SW, Portugal). The hypocenter was located at a shallow depth of 20 km. Primary telemetry verified by USGS/ISC-GEM.

Historical Landmark Earthquake

Curated Global Seismic Archive (1700–Present)

Top-100 Earthquakes

Magnitude 8.5 historical earthquake occurring on 1755-11-01 in Portugal. Associated with the Gorringe Bank Thrust (Thrust). Documented casualties: 60,000.

Documented Fatalities60,000

Fault KinematicsThrust

Equivalent Energy84.80 Mt TNT

Magnitudo

M 8.5

84.80 Mt TNT

Profondità

20 km

shallow (Crostale superficiale)

Impatto PAGER

red

60,000 fatalities

Feriti: > 5,000 · ~51.4M avvertito

Mappa interattiva di epicentro e faglie

36.00°N, 11.00°W

Faglia5 km

Gorringe Bank Thrust

Thrust · ~15.0 mm/yr

Felt byMMI III+

~51.4M exposed

~10.5M strong shaking

Primary SolutionUSGS/ISC-GEM

USGS/ISC-GEM#lisbon1755_benchmarkreviewed

1 agencies reporting

Setting36.0°N

Portugal

Offshore / Marine rupture

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 (superficiale)35–70 km (intermedia)>70 km (profonda)Scossa principale

Verified Disaster & Impact Assessment

Official emergency management data cross-checked against multi-agency wires

Continuous verification

Casualties

None expected (offshore epicenter)

Zero exposed population

Tsunami Status

TSUNAMI WARNING

NOAA PTWC & regional buoys

Citizen Felt Reports

Not felt / offshore epicenter

Macroseismic DYFI verification

Aftershock Sequence

Monitoring

Aftershocks expected (Omori law)

LightGBM hazard model forecast

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	M8.5(Mw)Ref	20.0 kmRef	36.00°, -11.00°Origin	Authoritative	lisbon1755_benchmark

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

2 centri abitati

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

Town	Distance	Intensity	Popolazione
Portimão · Faro	254 km	MMI VII	61,226
Faro · Faro	297 km	MMI VII	41,355

Tectonic setting

Nearest mapped active fault: Gorringe Bank Thrust, 5 km away, slip rate ~15.0 mm/yr (GEM Global Active Faults).