2/15/2016 — West Coast / California Volcano struck by M3.8 earthquake — Mammoth Mountain + Long Valley Caldera

A noteworthy M3.8 earthquake has struck near Mammoth Mountain Volcano, which is located in the large volcanic fields of the Long Valley Caldera + Mono Lake Supervolcano along Eastern California border with Nevada.

UPDATE 100pm CT (11am PT):

Another M3.5 earthquake has struck the same location approximately 3 hours after the M3.8 event.

M3.8 earthquake mammoth mountain volcano california Feb 15 2016

M3.5 long valley mammoth mountain feb 15 2016

Mammoth Mountain volcano has not erupted in over 700 years, however (luckily) this seismic event near the dormant volcano(es) is a sign of greater craton pressure, and building pressure off the West coast.   It is a sign of a coming earthquake off the coast (up the coast)…. not a sign of an impending eruption… at least not in the near term.

Normally, we see dormant volcanoes at the CA / NV border move in the days (sometimes hours) BEFORE we see movement off the nearby coast.

Pressure builds in the region, coming from BELOW the plate, and pushes to the East / Southeast.   This pressure builds and spreads out across the whole Western portion of the plate over a matter of days to weeks.

As the pressure builds, it finds the weakest spots to release along its way up from below.  The pressure hits the dormant volcanic chambers as it comes up while moving East.  This causes the volcanic chambers to move along the Eastern border of California before we see a larger event strike off the West coast.

I’ve covered this topic regarding California dormant volcanoes showing movement too many times to list here, thus here is the search for the topic in general, in case you’re curious about this subject:




Information on these earthquakes from the USGS:

Magnitude/uncertainty 3.8 ml± 0.3
Location/uncertainty 37.572 °N 118.858 °W± 0.2 km
Depth/uncertainty 5.3 km± 0.6
Origin Time
Number of Stations 34
Number of Phases 32
Minimum Distance 5.20 km (0.05°)
Travel Time Residual 0.04 sec
Azimuthal Gap 98°
Magnitude/uncertainty 3.5 ml± 0.4
Location/uncertainty 37.576 °N 118.856 °W± 0.2 km
Depth/uncertainty 5.3 km± 0.5
Origin Time
Number of Stations 43
Number of Phases 41
Minimum Distance 2.87 km (0.03°)
Travel Time Residual 0.06 sec
Azimuthal Gap 86°