Tuesday, July 9, 2019

Small Quake Swarm SW Of Mount Hood


A small seismic sequence of quakes is occurring on the SW flank of Mount Hood, Oregon today, with the largest quakes registering at magnitude 2.1. Around 60 quakes (at the time of this writing) have been registered so far. USGS CVO reports that this is likely purely tectonic in nature and is not the result of magma movement.

"On the afternoon of July 8, 2019 a swarm of small earthquakes started near Mount Hood, Oregon. As of 11:00 AM PDT on July 9, the Pacific Northwest Seismic Network has located more than 30 earthquakes, all occurring about 1 mile ENE of Government Camp and about 5 miles south of the Mount Hood summit. The earthquakes are relatively shallow (2-3 miles) and are likely too small (maximum magnitude 2.1) to be felt. Swarms in this area have occurred multiple times over the past two decades, most recently in 2014, with the largest event being a M 2.9 on September 14, 2001.

The largest event ever recorded near Mount Hood was a M 4.5 on June 29, 2002, at a location 3 miles south of the summit. Based on similarity to past seismic sequences near Mount Hood and on past studies of seismicity in the Mount Hood area, we infer that these earthquakes are occurring on tectonic faults and are not directly related to volcanic processes occurring beneath Mount Hood. http://ow.ly/PqBZ50uWRtz Mount Hood earthquake map: http://ow.ly/GY6u50uWRtI PNSN TDH webicorder http://ow.ly/n1xk50uWRtA"

Mount Hood, along the Cascades arc of volcanoes, was last confirmed to have erupted in 1865 with an unconfirmed eruption in 1869, according to the Smithsonian GVP.

Friday, July 5, 2019

Large Quake Sequence Hits Southern California

A large sequence of temblors is striking Southern California at the moment. This sequence so far is tectonic, not volcanic in origin, however it is striking very close to two dormant volcanic fields: The Coso Volcanic Field, and the Lava Mountains Volcanic Field.

The first major temblor, a magnitude 6.4 quake, spawned many aftershocks along the adjascent fault lines on 7/4/2019, and the second, larger shock struck at very shallow depth to the NW, at a magnitude of 7.1. Multiple aftershocks have since occurred, closer to the epicenters of the Coso Volcanic field, with the largest so fat at magnitude 5.5.

What this means for the area is not known. If this is purely a tectonic sequence, not much damage should occur outside of the immediate area. The Coso Volcanic Field has active geothermal power plants, and a few military installations.

The last identified eruptive period in this area was some 33,000 years ago, although suspected Holocene centers are inferred through morphology. It is tough to gauge the age of these volcanoes due to the desert climate, which can make older volcanism look younger than it actually is.

Google Earth screenshot with USGS quake overlay, and my volcano database.

More, larger quakes are possible. As has been theorized in the past, large quakes at the Southern end of the San Andreas fault line can propagate to the NW, creating a chain of events, although it is far too soon to see if this is the case.

Earthquakes, fault lines, and volcanic systems can and have interacted with each other in the past, however, given the age of the last eruption at the Coso Volcanic Field, an eruption still remains highly unlikely to occur. 

Residents in the vicinity should check their preparedness plans, and have an evacuation kit ready, if necessary, in the event of a larger quake.

Scientists in CA have long stated that CA is locked and loaded for 'The Big One" a quake of 8.0-9.0 in magnitude - and have advised that people have a plan in case of this event. California on average has had a large quake of 8.0 or more every 100 years or so, and for this, they are overdue.

It is important to note that USGS requires ample time to study each significant event, review the waveforms, and study factors like depth, whether these are purely fault slips, and whether subsequent events are purely tectonic in nature. No conclusions can be reached until all the data is in. Again, it is unlikely that this sequence would result in an eruption of nearby volcanic systems, but this is not unprecedented.

******UPDATE 7/8/2019*****

USGS CALVO Released the following statement regarding the Coso Volcanic Field:

"July 06, 2019 An earthquake swarm started on the evening of July 5 at the southern margin of Coso Volcanic Field in Inyo County, California. The swarm activity was triggered by a magnitude M5.4 earthquake at 9:19 PM PDT located 20 km (~20 miles) ESE of Little Lake, which itself was likely an aftershock of the M7.1 earthquake that occurred about an hour earlier 17 km NNE of Ridgecrest, and south of the Coso area. An average of about 30 earthquakes per hour have been detected since, most within the range of magnitude M1 to M3. No ground deformation indicative of volcanic activity has been detected, and there is no imminent threat of an eruption. The California Volcano Observatory will continue to monitor the situation for any sign of volcanic activity and provide updates as warranted.

The Coso Volcanic Field is located on the eastern side of the Sierra Nevada mountains at the northern end of the Mojave Desert, about 64 km (~40 miles) north of Ridgecrest. The field covers about 150 square miles primarily within the Naval Air Weapons Station at China Lake, and is comprised of lava domes, lava flows, and cinder cones erupted over the past 250,000 years. The most recent eruption was about 40,000 years ago."

Many large earthquakes have hit California in it's very long history. While this can and does create a lot of quake activity near the field, the 'crystal mush' in the magma chamber would still need fresh injection of magma into its chamber to trigger an eruption.

While Coso is not a good candidate for eruption, other volcanoes around the world remain 'primed', or close to an eruption, and a large earthquake sequence could indeed initiate an eruptive event. One such volcano is Mt. Fuji in Japan, which, according to Japanese authorities, is pressurized, and a large earthquake along its intersecting fault line could weaken the pressure on the chamber, thus causing an eruption. 

Wednesday, July 3, 2019

Stromboli Has Large Explosion, One Confirmed Dead


A large eruption has left one tourist dead, and several injured, also prompting evacuations on the island of Stromboli in the Aeolian Islands in Italy. Stromboli has frequent minor eruptions, but reports indicate this was a paroxysmal eruption with large amounts of ash fall. Lava emission was reported from all five summit vents preceding the explosive activity.

A large plume and pyroclastic flow seen from neighboring area. 
Photo credit Amelia Morris

According to some reports, two large explosions and over two dozen smaller ones have occurred. Hot ash fall caused several wildfires, and local firemen responded. Boats from neighboring islands have been making their way to assist with the evacuation of the town of Ginostra on the WSW side of the island, where tourists were reportedly hiding in the ocean to escape the hot ash.

Residents on the nearby island of Panarea reported fear of tsunami, and evacuating to higher elevations, however no tsunami was generated by this event.

This is possibly the largest explosive event on Stromboli since the year 2007, however the volcano has been in continuous eruption since Feb 2, 1934, according to the Smithsonian GVP. The activity appears to have declined dramatically after the large explosions and is apparently returning to 'normal' at this time.

Known widely as "The Lighthouse of the Mediterranean", the volcano has reliably lit up the night sky with explosive lava fountains and lava emissions throughout most of historical time, and is a reliable place to witness an active volcanic eruption. Strombolian eruptions are named for the volcano and is used as a baseline comparison for similar eruptive events at similar volcanoes.

Tuesday, July 2, 2019

HVO Raises Mauna Loa Alert Level To Yellow (Watch)


The Hawaiian Volcano Observatory (HVO) raised the alert code to yellow (advisory) and the aviation code for Mauna Loa today to Yellow due to increased rates of inflation and seismicity under the summit and Soutwhest Rift zone. Deformation data since the end of the Kilauea eruption shows a steady increase in inflation.

Screengrab from HVO's Mauna Loa monitoring page.

HVO reports:

"For the past several months, earthquake and ground deformation rates at Mauna Loa Volcano have exceeded long term background levels. An eruption is not imminent and current rates are not cause for alarm. However, they do indicate changes in the shallow magma storage system at Mauna Loa.

Following a significant earthquake swarm in October 2018, HVO seismic stations have recorded an average of at least 50 shallow, small-magnitude earthquakes per week beneath Mauna Loa's summit, upper Southwest Rift Zone, and upper west flank. This compares to a rate of fewer than 20 per week in the first half of 2018. Shallow earthquakes are occurring in locations similar to those that preceded Mauna Loa's most recent eruptions in 1975 and 1984.

During this same time period, GPS instrumentation and satellite radar have measured ground deformation consistent with renewed recharge of the volcano's shallow magma storage system. The current rate and pattern of ground deformation is similar to that measured during inflation of Mauna Loa in 2005 and again from 2014 - 2018.

Together, these observations indicate the volcano is no longer at a background level of activity. Accordingly, HVO is elevating the Mauna Loa alert level to ADVISORY and the aviation color code to YELLOW.

Alert levels and aviation color codes are explained here: https://volcanoes.usgs.gov/vhp/about_alerts.html 

This increase in alert level does not mean that an eruption is imminent nor that progression to an eruption is certain. A similar increase in activity occurred between 2014 and 2018 and no eruption occurred."

Mauna Loa, towering over Kilauea, is one of the most active volcanoes on the Big Island of Hawaii, and last erupted in 1984 in conjunction with resumed activity from Kilauea, however it has been dormant (but restless) since then.

An eruption from Mauna Loa could put structures at risk, due to it being one the of the largest shield volcanoes in the world, coupled with fast moving basaltic lavas.

Footage of previous Mauna Loa Eruption

HVO continues:


As has happened before, it is possible that current low-level unrest will continue and vary in intensity for many months, or even years without an eruption. It is also possible that the current unrest is an early precursor to an eventual eruption. At this time, we cannot determine which of these possibilities is more likely.

HVO expects that days or weeks prior to an eruption, monitoring instruments will detect signs of an increased potential for eruption. These signs could include further increases in rates of earthquakes and ground deformation, increases in the sizes of earthquakes, an increase in surface temperatures, or an increase in visible steam plumes or sulfur dioxide emissions.

However, it is also possible that the timeframe to eruption could be shorter - hours to days. All communities on the flanks of the volcano should be prepared.

HVO continues to monitor the volcano closely and will report any significant changes. HVO is in close touch with Hawaii County Civil Defense and other agencies responsible for public safety.

Stay informed about Mauna Loa by following volcano updates and tracking current monitoring data on the HVO web page (http://hvo.wr.usgs.gov/activity/maunaloastatus.php) or by signing up to receive updates by email at this site: http://volcanoes.usgs.gov/vns/

Hawaii County Civil Defense Agency is in constant communications with HVO. If anything develops that may affect your safety, you will be informed.

Please sign up for Civil Defense notifications by visiting Hawaii County Civil Defense Agency webpage at http://www.hawaiicounty.gov/civil-defense/."

Due to this upgrade in status to Yellow, HVO will now be issuing weekly instead of monthly updates on the volcano.

It had been rumored for some time that HVO would be looking more closely at Mauna Loa after the end of eruptive activity from Kilauea, and the increased activity has been going steady since the end of that eruption. The steady rate of inflation coupled with many small quakes, and some over 3.0 in magnitude over the past year is the cause for this concern.

The eruption in 1984 crossed several roads, and threatened the town of Hilo. Development on the island since that eruption will increase the likelihood that Mauna Loa will be a threat to property. However as with most eruptions on Hawaii, it is rare that lives are threatened, except of course for the last eruptive episode on Kilauea, which resulted in a fissure system opening under a neighborhood. While some injuries did occur, no lives were lost.

The current activity seems to be centered however on the opposite side of the volcano from the 1984 eruption, which occurred on the NE rift zone and summit caldera. The current focus of seismicity seems centered on the summit caldera, and the Southwest Rift zone. This could threaten the mountainside neighborhood of Ocean View, which resides on old flows from the SWRZ, the town of Pahala (surrounded by farmland), and Naalaehu. The most likely scenario should a SWRZ eruption occur would be encroachment of lava to Ocean View, however it is far too soon to speculate.

Residents should pay close attention to HVO alerts and updates, and have a preparedness plan should Mauna Loa erupt with short warning. As was the case with the Kilauea eruption, you'd likely have weeks, days, or hours of clear signs before an eruption will be declared imminent, as this is one of the best monitored volcanoes in the world.