Cascadia Subduction Zone Map

Last updated 11 October 2026

What the map shows

The thick blue line offshore is the Cascadia subduction zone Subduction zone. Where one plate sinks under another and back into the mantle, usually marked by a deep ocean trench. Source , the boundary where the Juan de Fuca Plate sinks under the North American Plate. It is the northeast corner of the Ring of Fire. Dashed lines are the other plate boundaries: the Gorda, Juan de Fuca and Explorer ridges where new sea floor forms, and transform faults. In the south, the San Andreas fault links these ridges to the East Pacific Rise.

Red dots are volcanoes from the NOAA database: the Cascade Range on land and ridge segments offshore. Orange dots are earthquakes from the NOAA significant earthquake list, sized by magnitude. Gray lines on land are USGS Quaternary faults. The great 1700 earthquake is drawn at the position NOAA gives it, 45°N 125°W, but it broke a long stretch of the zone.

Key facts

1. In the PB2002 model the subduction zone is 1,415 km long, from 40°N, 125°W off northern California to 52°N, 131°W near the north end of Vancouver Island. Bird (2003)
2. The model has the plates converging at about 4.0 cm/yr. About 7 in 10 subduction boundary steps on Earth move faster. Bird (2003)
3. The last great earthquake struck on 27 January 1700 (UTC), magnitude 9 in the NOAA database. NOAA NCEI significant earthquakes
4. Its tsunami crossed the Pacific. NOAA records it at 7 places in Japan, with waves up to 5.4 m high at Miho, and 2 deaths there. NOAA NCEI Global Historical Tsunami Database
5. People in Japan wrote down the flooding in January 1700 but felt no earthquake. Scientists linked this "orphan tsunami" to Cascadia only in the middle 1990s. Atwater and others, The orphan tsunami of 1700 (USGS Professional Paper 1707)
6. Since 1851, the largest earthquake in the map area was magnitude 7.6 (California: Northern, 1922). The deadliest earthquake was the 1949 magnitude 7 event (Washington), with 8 deaths. NOAA NCEI significant earthquakes
7. 36 volcanoes on land in the NOAA database lie in the map area, 226 to 384 km from the subduction zone line. The highest is Rainier, 4,392 m. 10 more are ridge segments on the sea floor. NOAA NCEI Volcano Locations Database

Significant earthquakes in the region

Every event in the NOAA significant earthquake database inside the map area (131 to 119°W, 39 to 52°N). NOAA lists an event when it caused about $1 million of damage or more, 10 or more deaths or a tsunami, or reached magnitude 7.5 or more. Sort by any column.

Data source: NOAA NCEI Global Significant Earthquake Database, Public domain (US Government work). Download: CSV .

Volcanoes of the Cascades

On land, the volcanoes stand 226 to 384 km east of the subduction zone line, from northern California to British Columbia. Below sea level are the spreading ridge segments. Highest first.

Data source: NOAA NCEI Volcano Locations Database, Public domain (US Government work).

The 1700 earthquake and tsunami

The tsunami Tsunami. A series of sea waves set off by an earthquake, an undersea landslide or, less often, an island volcano. Not related to tides. Source of January 1700 reached Japan, where samurai, merchants and villagers wrote of flooding and damage. Some noted that no earthquake had been felt. Only in the middle 1990s did scientists link these waves to an earthquake on the Cascadia subduction zone. NOAA's tsunami database lists 7 places in Japan with observations, waves up to 5.4 m high and 2 deaths. The NOAA list has no earthquake of magnitude 8 or more in the map area since.

Data source: NOAA NCEI Global Historical Tsunami Database, Public domain (US Government work).

History: Atwater and others, The orphan tsunami of 1700 (USGS Professional Paper 1707).

Download

cascadia-significant-earthquakes.csv lists the earthquakes in the table above, from NOAA NCEI (public domain). The volcanoes are in volcanoes-ncei.csv and the faults in us-quaternary-faults.geojson. The plate boundary is from PB2002 (ODC-By 1.0).

Related: the subduction zones map, the US fault lines map, the volcano map and the live earthquake map.