Shallow M5.8 earthquake registered 180 km S of Axial Seamount, off the coast of Oregon


A shallow earthquake registered as M5.8 hit off the coast of Oregon, US at 06:52 UTC on June 1, 2015. USGS is reporting a shallow depth of 10 km (6.2 miles).

Epicenter was located about 180 km (113 miles) S of submarine volcano Axial Seamount and 514 km (319 miles) W of Dallas, Oregon.

There are no people living within 100 km radius and tsunami was not expected.

USGS issued green alert for shaking-related fatalities and economic losses. There is a low likelihood of casualties and damage.

At 07:01 UTC, an aftershock with recorded magnitude of 4.3 was registered in the same region (depth 10km/6.2 miles).

Image credit: USGS.


At 20:11 UTC, USGS recorded M5.9 earthquake in the same area at the same depth.

Image  credit: USGS

  1. 4.2Off the coast of Oregon2015-06-02 03:11:25 UTC10.0 km
  2. 3.9Off the coast of Oregon2015-06-02 02:50:44 UTC10.0 km
  3. 5.9Off the coast of Oregon2015-06-01 20:11:31 UTC10.0 km
  4. 4.4Off the coast of Oregon2015-06-01 14:46:34 UTC10.0 km
  5. 5.5Off the coast of Oregon2015-06-01 10:46:27 UTC10.0 km
  6. 4.3Off the coast of Oregon2015-06-01 07:01:20 UTC10.0 km
  7. 5.8Off the coast of Oregon2015-06-01 06:52:41 UTC10.0 km
  8. 1.214km NW of Brookings, Oregon2015-05-26 20:07:21 UTC14.3 km
Data source: USGS (updated at 07:02 UTC on June 2)

**end of update**

Geologists reported that starting at 22:30 local time on April 23 thousands of small earthquakes were detected at the Axial Seamount, and then the seafloor dropped by 2.4 m over a three-day period. It was unclear if the earthquakes and deflation meant an eruption or a large intrusion of magma that did not reach the surface.

Axial Seamount rises 700 m above the mean level of the central Juan de Fuca Ridge crest about 480 km (298 miles) west of Cannon Beach, Oregon to within about 1 400 m of the sea surface. The volcano is the most magmatically robust and seismically active site on the Juan de Fuca Ridge between the Blanco Fracture Zone and the Cobb offset.

Map of Juan de Fuca Ridge – Gorda Ridge – Axial Seamount – Blanco facture zone — showing features of Pacific/Juan de Fuca/North American subduction system relative to Western United States. Open blue arrows, ridge-spreading directions; solid blue arrow, convergence direction. — Modified from: Swanson, et al., (1989)IGC Field Trip T106: Cenozoic Volcanism in the Cascade Range and Columbia Plateau, Southern Washington and Northernmost Oregon, p.2 Redrawn as SVG with enhancements.

The summit is marked by an unusual rectangular-shaped caldera (3 x 8 km) that lies between two rift zones and is estimated to have formed about 31 000 years ago. Detailed mapping and sampling efforts have identified more than 50 lava flows since about 410 AD (Clague et al., 2013). Eruptions producing fissure-fed lava flows that buried previously installed seafloor instrumentation were detected seismically and geodetically in 1998 and 2011 and confirmed shortly after each eruption during submersible dives.

Exaggerated swatch bathymetry of Axial Seamount. Image credit: NOAA.

Axial Seamount was first detected in the 1970s by satellite altimetry, and mapped and explored by Pisces IV, DSV Alvin, and others through the 1980s. A large package of sensors was dropped on the seamount through 1992, and the New Millennium Observatory was established on its flanks in 1996.

The volcano received significant scientific attention following the seismic detection of a submarine eruption at the volcano in January 1998, the first time a submarine eruption had been detected and followed in situ. Subsequent cruises and analysis showed that the volcano had generated lava flows up to 13 m (43 feet) thick, and the total eruptive volume was found to be 18,000–76,000 km3 (4,300–18,200 cu miles). Axial Seamount erupted again in April 2011, producing a 1.6-km wide (1 mile) lava flow and fulfilling a 16-year cycle that had been predicted in 2006.

Featured image: Google Earth/USGS. © 2010 Google.

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