Strong Quake Swarm SSW of Cerro Prieto, Mexico

A minor swarm of earthquakes hit several miles SSW of Cerro Prieto in Mexico, near the US border (and my hometown of San Diego County). The largest quake was measured at 4.7 by USGS, however there were two subsequent tremblors of 4.6, and 4.1, as well as many magnitude 3 and under. This occurred along the same fault line that eventually transforms into the San Andreas fault, and begins between mainland Mexico, and Baja California, Mexico.

No damage has been reported so far.

The epicenters of the quakes are several miles south of the epicenter of the last large quake in the region, (a 7.4 magnitude quake in 2010 that was dubbed "The Easter Quake). I was present very near the epicenter and experienced this firsthand. The current quake swarm is likely a result of this quake, as the region has experienced many minor to somewhat large tremors since the Easter Quake. This is most likely due to crustal adjustments, and settling, and not a precursor toward volcanic eruption. However just NW of the epicenter lies a more than 10,000 year old small volcano cone name Cerro Prieto. Just NNW of that cone, lies the Salton Sea, another volcanic center which has also experienced Holocene eruptions, and is, as well as Cerro Prieto, an actively producing geothermal field.

The GVP describes local Cucapas Indian legends of a monster rising from the earth and emitting "Fire tongues", which has been interpreted to mean a description of the growing volcano in its infancy. While neither Cerro Prieto nor the Salton Sea has seen any volcanic activity during recent historical times, it is an area that will likely have an eruption in the earth's future. Current displays of volcanic activity can be found at the Salton Sea by way of fumeroles, and mud volcanoes, as well as the geothermal power plants in the area. In the Cerro Prieto region, geothermal plants dot the area, and during some quakes, it has been reported that spouts of sulfuric smelling water, red in color, emanate from the landscape like geysers, however only briefly.

During the 7.4 magnitude quake, the area was lightly reported to have had increased surface activity from geothermal forces.

The activity in the area is caused by light crustal spreading, and impaction northward. As the plate grind North, they also spread slightly at the Pacific/North American Plate boundary, near San Diego, CA, pulling Baja California away from mainland Mexico, yet upwards toward the mainland USA.

The current quakes are not volcanic in nature, however the area will someday experience eruptive activity. In the near future however, this is not likely to happen.

El Hierro Island Uplifted Several Centimeters

The earthquake swarms are continuing at El Hierro, months after the submarine eruption ended, and has caused new inflation of the island. Uplift and displacement of up to 5cm has now occurred since the beginning of the month, suggesting that deep underground, new magma is indeed being injected to the deep magma reservoir under the island. INVOLCAN scientists, according to Earthquake-report.com are staying on the island for the next 30 days, at their own expense, despite the Spanish government keeping the volcano at alert level 'green'. It seems the scientific community disagrees.

While today's activity is a bit lower than the past couple of days, the previous activity at the volcano (for those that were following it) appeared to be random and have some high and low periods of seismicity. If the same deep magma mechanism is in place, and injection is still occurring, you can expect bursts of strong activity accompanied by randomized weaker activity.

The seismicity is even in the same place as when the island built up for the last eruption. It is not far fetched at this point to assume that an eruption could be a couple of months, or even weeks away, but so far these quakes have been deep, and no new CO2 emission increases or other signs of impending volcanic activity have so far been observed. Right now all that is certain is that about 20-15km below the island, magma is re-inflating the chamber. If this continues for some time, this might indicate an eruption is about to take place again in the future. If it ceases, the magma may simply stir a while and cool slowly.

El Hierro is once again a place to watch on the list of active volcanoes.

*****UPDATE 7/2/2012******

This morning there was another hour long period of heightened seismicity, producing several quakes that were felt by residents. The new center of activity is at the NW tip of the island, partially on and partially off the coast. So far, the alert level remains the same. GPS graphs showed slight subsidence taking place BEFORE the quakes started (we are waiting for the post swarm data from Earthquake-report.com, which is one of the only blogging sites on the 'net with boots on the ground).

Earthquake activity is still much stronger than in past weeks, but currently it does not appear to be getting much stronger, and if anything, it might be getting weaker. It is still far too soon to tell whether or not the seismicity portends a future eruption of the island.

UPDATE:

Earthquake activity has returned and has now been sustained for up to 6 hours. Many quakes are above 3.0.

Alaska's Mt Spurr Has Glacial Outburst Flood

Alaska's mt Spurr volcano, which last erupted in 1992, depositing ash on nearby Anchorage, AK, had a glacier outburst flood (or jökullhlaup if you like the Icelandic tongue twister) which lasted about 45 minutes after a period of weak, shallow quakes. This is pretty common in a lot of glacier-clad volcanoes, and especially in Iceland where geothermal activity routinely melts water under a glacier's surface, which results in a 'burst' of water escaping, causing sudden floods.

This does not mean the Spurr is gearing up for an eruption, as this could merely be normal behavior for the volcano (as also occurred in 1993, with no subsequent eruption), however this is one of the signs that volcanologists look for as a potential warning. If for example, the volcano began to do this rather regularly, there might be cause for concern. For now AVO has not raised the alert level, and probably will not unless the event repeats itself.

AVO's report is below:

"SPURR VOLCANO
61°17'56" N 152°15'14" W, Summit Elevation 11070 ft (3374 m)
Current Volcano Alert Level: NORMAL
Current Aviation Color Code: GREEN

Early on the morning of June 25 a minor increase in seismicity occurred at Mount Spurr. The character of the seismicity recorded was consistent with the seismic energy generated by an energetic flow of water, possibly a glacier outburst flood on the lower south flank of Mount Spurr. The flow was a single event lasting about 45 minutes and was associated with several discrete shallow earthquakes up to magnitude 1 in size. Within hours of the onset, seismic levels declined to near background and no additional flowage signals were observed. Visitors to the area were advised to use caution if in or around the drainages on the south flank of Mount Spurr, especially those draining Kidazgeni glacier, and the Chakachatna River east of Kidazgeni Creek. A similar flowage event occurred on June 29, 1993.

Mount Spurr volcano is an ice- and snow-covered stratovolcano located on the west side of Cook Inlet approximately 120 km (75 mi) west of Anchorage. The only known historical eruptions occurred in 1953 and 1992 from the Crater Peak flank vent located 3.5 km (2 mi) south of the summit of Mount Spurr.

These eruptions were brief, explosive, and produced columns of ash that rose up to 20 km (65,000 ft) above sea level and deposited several mm of ash in south-central Alaska, including approximately 6 mm of ash on Anchorage in 1953. The last known eruption from the summit of Mount Spurr was more than 5,000 years ago. Primary hazards during future eruptions include far-traveled ash clouds, ash fall, pyroclastic flows, and lahars or mudflows that could inundate drainages all sides of the volcano, but primarily on the south and east flanks."

Antarctic Volcano, Siple Shows Signs Of Activity

You don't normally hear much from the land way, way down under given the very low human presence in Antarctica, but today the GVP reports that the Antarctic stratovolcano Siple is showing geothermal signs. This was confirmed via satellite imagery which observed vapor plumes and temperature variations at the summit of the massive volcano. If confirmed, this would be the first credible evidence on record for historical activity at the volcano. While the volcano has been studied and determined to be Holocene of age, it has not had any confirmed activity since it has been discovered, and a potassium-argon date is unavailable for its apparently most recent eruption.

The GVP describes this volcano as follows:

"Mount Siple is a youthful-looking shield volcano that forms an island along the Pacific Ocean coast of Antarctica's Marie Byrd Land. The massive 1800 cu km volcano is truncated by a 4-5 km summit caldera and is ringed by tuff cones at sea level. Its lack of dissection in a coastal area more susceptible to erosion than inland Antarctic volcanoes, and the existence of a satellite cone too young to date by the Potassium-Argon method, suggest a possible Holocene age (LeMasurier and Thomson 1990). The location of Mount Siple on published maps is 26 km NE of the actual location. A possible eruption cloud observed on satellite images on September 18 and October 4, 1988 was considered to result from atmospheric effects after low-level aerial observations revealed no evidence of recent eruptions (Smithsonian Scientific Event Alert Network Bulletin)."

The current statement from the GVP as of today's weekly report:

"Infrared imagery from the Metop satellite showed a possible rising steam plume from the area of Siple on 20 June. The imagery, as interpreted by Mark Drapes, indicated that the volcano was about -22 degrees Celsius, about 6 degrees warmer that the surrounding landscape, and the base of the plume was about -55 degrees Celsius."

While this report is not definitive proof that the volcano is erupting or preparing to erupt, it could indicate some unrest. The only evidence whatsoever so far that it is an active volcano is the 6 degrees Celsius differential from the surrounding area, and what appears to be steam from a satellite view. Until scientists or an expedition can have visual proof from the ground, this could end up being something like the 1988 'episode' that ended up to be an error. No worries however, as the volcano exists in one of the most remote places on earth, with not a human being in sight for thousands of miles.

El Hierro Not Finished Yet?

The volcanic island of El Hierro, part of Spain's Canary Islands, is showing increased signs that it is again gearing up for some activity. According to IGN and Earthquake-report.com, there were over 104 magnitude 2 or above quakes at the island yesterday alone. This is on par with the amount of quakes that preceded the previous and all but over eruption of the submarine volcano off the coast of the town of La Restinga. The below YouTube Video is an animation of the quakes in sequence and magnitude.

The activity currently being experienced is almost certainly related to further dike intrusion underneath the volcano, and a likely precursor to future activity on the island. The Spanish government had previously declared the eruption over, despite occasional underwater bursts from the small submarine cone that was constructed over around a year. Harmonic tremor had all but disappeared, leaving only a weak signal. But the volcano never truly stopped its activity. Degassing and other emissions are still ongoing, and those who know are still certain that El Hierro is far from done.

The location of the current swarm of quakes suggests that next time El Hierro erupts, it might not be underwater this time. So far, Pevolca, INVOLCAN, and IGN have all been mum on the quakes, saying only that they are monitoring the situation in real time. It is of some concern that the small cone which has ceased erupting is probably blocked form doing so again, so the question now is where can/will the magma release? If it can't go the same direction, it will go another.

At last glance, the quakes are still ongoing, with some above magnitude 3.0. If they rise to 4.0, 5.0, or higher, the island may very well have another situation on their hands. I will return to active monitoring of this volcano, as it appears things are changing quickly. The below photo is a real time (for today) seismic graph. It's starting to look pretty familiar.