Earthquake Near Anchorage

ANCHORAGE, Alaska – A strong earthquake jolted a swath of southern Alaska on Monday, sending people diving under desks and huddling in doorways but causing little damage.

The U.S. Geological Survey said the 5.4 magnitude tremor struck about 24 miles from the town of Willow at 11:28 a.m. The rumbling lasted several moments in Anchorage, 58 miles from the epicenter, and was felt as far south as Kenai and north to Fairbanks, a span of 300 miles.

...Monday's earthquake and its aftershocks had nothing to do with Mount Redoubt, Alaska's most active volcano with a series of explosions earlier this year. Dave Schneider, a geophysist at the Alaska Volcano Observatory, said the volcano's seismic instruments more than 100 miles from the epicenter picked up the temblors, which he enjoyed from his Anchorage office.

"I thought it was kind of fun, but I'm like that," he said.

Geeks are like that.

I'd say more, but I'm with him. It would be kind of fun...

Bombay Beach is Shaking

Following a moderate earthquake on Tuesday, an ongoing swarm of small earthquakes has continued to shake the area around the Salton Sea in southern California.

Right now, this earthquake swarm is getting the attention of seismologists, due to both their frequency and especially their location, which is very close to a segment of the San Andreas Fault that is believed to be overdue for a major earthquake. The Southern California Seismic Network has a report on the swarm up on their main page.

The main response is one of "We need more info." Additional seismographs and other sensors are being emplaced around the area, in order to better determine the location of the quakes and find if there is any pattern to them. (For instance - are the locations of the quakes trending in any direction?) It is important to note that this swarm is not that unusual - a similar swarm occurred in 2001. But it bears watching.

There also seems to be some increased alertness among emergency planners. The California Office of Emergency Services issued a notice yesterday, advising of the earthquake swarm and encouraging officials to review their emergency plans.

This area is very interesting, seismologically. Somewhere near the Salton Sea and heading southeast through the Imperial Valley, the San Andreas Fault becomes less defined, broadening into a rift zone where the North American plate and the Pacific Plate stop sliding past each other and actually start moving away from each other. These quakes are occurring about where this rift zone begins.

For more information:

Southern California Seismic Network

USGS, "Recent Earthquakes in California and Nevada"

Los Angeles Times, "Salton Sea is swarming with earthquake data"

Los Angeles Times, "Study finds troubling pattern of Southern California quakes"

The Earthquake Swarm is Over

For now, at least.

The earthquake swarm under Yellowstone Lake has apparently drawn to a close. The last week's worth of reports show a return to near-quiescence.

The Yellowstone Volcano Observatory has an excellent poster [warning: big PDF at link]summarizing and contextualizing the swarm. The poster puts the quake swarm into the larger picture - a fascinating and complex picture.

New Articles on Yellowstone Earthquakes

The Yellowstone Volcano Observatory has released a new in-depth article and podcast discussing the recent earthquake swarm under Yellowstone Lake. The article doesn't reveal any new analysis, but does provide an excellent summary of the earthquakes up to now and offers some helpful background information.

This Salt Lake Tribune article also provides some useful information; it suggests that scientists are leaning towards a geothermal explanation, but aren't ready to draw any formal conclusions yet.

We will probably have to wait a while for the analysis; with the swarm tapering off, at least for the moment, some of the urgency is gone, and the scientists can afford to make a more careful analysis. No obvious change in geyser or spring activity has been observed as yet; however a more careful survey will have to wait until spring.

Unanswered, for now, is whether these quakes are due to volcanic pressures, geothermal energy, or the more normal geophysical stresses of the faults in and around Yellowstone.

(The Yellowstone Park region is no stranger to earthquakes due to more familiar forces - one major quake happened west of the Park as recently as 1959. Personalizing the Earthquake Threat has more information.)

Yellowstone Lake Earthquakes - Jan.6th Update from YVO

The latest statement from the Yellowstone Volcano Observatory has some analysis and earthquake history that is very helpful.

Quoting their latest statement:

Through 5 January 2009, seismic activity has markedly decreased. It is possible that the swarm has ended, though a return of activity may occur as Yellowstone swarms of the size usually last for tens of days to many weeks.

About 500 earthquakes occurred between Dec. 26 through Jan. 1. Three hundred of the earthquakes (including all >M2.0) have been reviewed by seismologists. There have been 86 earthquakes with M > 2.0 and 16 earthquakes > M3.0. About 200 smaller earthquakes have yet to be reviewed. Depths are difficult to determine accurately. The best located earthquakes have depths on the order of 3 to 10 km (1.8 to 6.0 miles). From Dec. 26 through Jan 2, the earthquake hypocenters appear to have migrated northwards, starting southeast of near Stevenson Island, with many of the latest events occurring near Fishing Bridge.

The recent swarm is well above typical activity at Yellowstone. Nevertheless it is not unprecedented during the last 40 years of monitoring. Swarms are the typical mode of occurrence of earthquakes within the Yellowstone caldera, with magnitudes ranging to > 4.0. The 1985 swarm on the northwest rim of the caldera lasted for three months, with earthquakes up to M4.9 and over 3000 total events recorded.

Interesting. Most valuable, to my mind, is the discussion on the 1985 swarm, which provides some needed context.

It also suggests that, barring a sudden return in activity, that this is an event to notice, but not to worry about.

Yellowstone Lake Earthquake Swarm Tapering Off?

Today's earthquake map, current as of about 12 hours ago, shows a marked reduction in the frequency and severity of earthquakes located under Yellowstone Lake, a swarm of which had been ongoing for almost a week. This reduction in severity started about Jan. 2nd; the frequency started dropping on Jan. 3rd. It's too early to say what that means, or even if there is any significance to the swarm's slowing.

It would appear that seismologists and geophysicists are still trying to determine what the swarm meant in the first place. Judging from their press release, they are not too concerned about volcanic activity right now; it appears that geothermal activity (i.e. hot water, as opposed to hot lava) may be the culprit. There is a history of that at Yellowstone Lake. In addition to the geothermal features such as geysers, springs, mud pots, and fumaroles around the park, occasionally steam explosions of various sizes rearrange the topography. (Pretty much what it sounds like - steam builds up underground to the point that the rock constraining it shatters.) Parts of Yellowstone Lake's shoreline were carved out by steam explosions. From "Questions About Volcanic Activity at Yellowstone" on the Yellowstone Volcanic Observatory website,

The most likely type of eruption would not be volcanic but, rather, hydrothermal. This type of small, but still explosive eruption can occur from shallow reservoirs of steam or hot water rather than molten rock. These reservoirs are the sources of Yellowstone's famous geysers, hot springs, and fumaroles. Such explosions could blast out shallow craters more than a kilometer wide; as has occurred in the northern Yellowstone Lake Basin, including Mary Bay and nearby Turbid Lake and Indian Pond, and in western Yellowstone National Park north of Old Faithful. Each of these craters was produced by steam blasts within the past few thousand years.

So we more likely are seeing the beginnings of a steam explosion, rather than an active volcano. But that is not certain, yet. There's going to be a bunch of scientists spending a lot of hours studying seismograms before we hear any hypotheses.

There is agreement on point - there is nothing to panic about. Yet.

Geology, in action. Bring a lunch.

YELLOWSTONE VOLCANO OBSERVATORY INFORMATION RELEASE
Friday, January 2, 2009 19:30 MST (Saturday, January 3, 2009 02:30 UTC)

YELLOWSTONE VOLCANO (CAVW#1205-01-)
44.43°N 110.67°W, Summit Elevation 9203 ft (2805 m)
Volcano Alert Level: NORMAL
Aviation Color Code: GREEN

Yellowstone Lake Earthquake Swarm Update: 2 January 2008

The University of Utah Seismograph Stations reports that as of 1800 MST on 2 January 2009, seismicity of the ongoing Yellowstone earthquake swarm continues. Over 500 earthquakes, as large as M 3.9, have been recorded by an automated earthquake system since the inception of this unusual earthquake sequence that began Dec. 27, 2008. More than 300 of these events have been reviewed and evaluated by seismic analysts. Depths of the earthquakes range from ~ 1km to around 10 km. We note that the earthquakes extend northward from central Yellowstone Lake for ~10 km toward the Fishing Bridge area, with a migration of recent earthquakes toward the north. Some of the dozen M3+ earthquakes were felt in the Lake, Grant Village and Old Faithful areas. Personnel of the Yellowstone Volcano Observatory continue to evaluate this earthquake sequence and will provide information to the NPS, USGS and the public as it evolves.

This earthquake sequence is the most intense in this area for some years. No damage has been reported within Yellowstone National Park, nor would any be expected from earthquakes of this size. The swarm is in a region of historical earthquake activity and is close to areas of Yellowstone famous hydrothermal activity. Similar earthquake swarms have occurred in the past in Yellowstone without triggering steam explosions or volcanic activity. Nevertheless, there is some potential for hydrothermal explosions and earthquakes may continue or increase in magnitude. There is a much lower potential for related volcanic activity.

Yellowstone Lake Earthquake Swarm

A more recent update from the Yellowstone Volcano Observatory, with some useful links:

YELLOWSTONE VOLCANO OBSERVATORY INFORMATION RELEASE
Monday, December 29, 2008 19:07 MST (Tuesday, December 30, 2008 02:07 UTC)

YELLOWSTONE VOLCANO (CAVW#1205-01-)
44.43°N 110.67°W, Summit Elevation 9203 ft (2805 m)
Volcano Alert Level: NORMAL
Aviation Color Code: GREEN

Earthquake swarm beneath Yellowstone Lake continues.

PRESS RELEASE FROM YVO PARTNER UNIVERSITY OF UTAH SEISMOGRAPH STATIONS

Released: December 29, 2008 05:00 PM MST


The University of Utah Seismograph Stations reports that a notable swarm of earthquakes has been underway since December 26 beneath Yellowstone Lake in Yellowstone National Park, three to six miles south-southeast of Fishing Bridge, Wyoming. This energetic sequence of events was most intense on December 27, when the largest number of events of magnitude 3 and larger occurred.

The largest of the earthquakes was a magnitude 3.9 (revised from magnitude 3.8) at 10:15 pm MST on Dec. 27. The sequence has included nine events of magnitude 3 to 3.9 and approximately 24 of magnitude 2 to 3 at the time of this release. A total of more than 250 events large enough to be located have occurred in this swarm. Reliable depths of the larger events are up to a few miles. Visitors and National Park Service (NPS) employees in the Yellowstone Lake area reported feeling the largest of these earthquakes.

Earthquakes are a common occurrence in the Yellowstone National Park area, an active volcanic-tectonic area averaging 1,000 to 2,000 earthquakes a year. Yellowstone's 10,000 geysers and hot springs are the result of this geologic activity. A summary of Yellowstone's volcanic history is available on the Yellowstone Volcano Observatory web site (listed below). This December 2008 earthquake sequence is the most intense in this area for some years and is centered on the east side of the Yellowstone caldera. Scientists cannot identify any causative fault or other feature without further analysis. [In other words, they can't yet tell if this is due to magma movement, geothermal activity of some kind, or if the more typical forces behind earthquakes are behind this. - Tyler] Seismologists continue to monitor and analyze the data and will issue new information if the situation warrants it.

The University of Utah operates a seismic network in Yellowstone National Park in conjunction with the National Park Service and the U.S. Geological Survey (USGS). These three institutions are partners in the Yellowstone Volcano Observatory.

Data are transmitted to the University in real-time by radio and satellite links from a network of 28 seismographs in the Yellowstone area and are available on the web. Seismologists continue to analyze data from this swarm of earthquakes and provide updates to the NPS and USGS and to the public via the following web pages.

Information on U.S. earthquake activity including Yellowstone can be viewed at the U.S. Geological Survey web site: http://earthquake.usgs.gov/eqcenter/recenteqsus/

Information on earthquakes can also be viewed at the University of Utah Seismograph Stations web site:
http://www.seis.utah.edu/.

Seismographic recordings from Yellowstone seismograph stations can be viewed online at:
http://www.quake.utah.edu/helicorder/heli/yellowstone/index.html.

Persons who felt any of the earthquakes are encouraged to fill out a survey form on the USGS 'Did You Feel It?' web site: http://earthquake.usgs.gov/eqcenter/dyfi/.

Geologic information, maps, and monitoring information for Yellowstone can be found on the Yellowstone Volcano Observatory web site at:
http://volcanoes.usgs.gov/yvo/.



-----
The Yellowstone Volcano Observatory (YVO) is a partnership of the U.S. Geological Survey (USGS), Yellowstone National Park, and University of Utah to strengthen the long-term monitoring of volcanic and earthquake unrest in the Yellowstone National Park region. Yellowstone is the site of the largest and most diverse collection of natural thermal features in the world and the first National Park. YVO is one of the five USGS Volcano Observatories that monitor volcanoes within the United States for science and public safety.

I'm Not a Seismologist... (UPDATED)

"...but I did stay at a Holiday Inn Express last night."

Okay, so it was two weeks ago, and it was a Best Western, and I actually found out about it from the Drudge Report, but something interesting is happening in Yellowstone National Park.

[UPDATES BELOW. - T]

From the USGS Yellowstone Volcano Observatory:

The University of Utah Seismograph Stations reports that a swarm of small earthquakes of magnitude 3.5 and smaller is occurring beneath Yellowstone Lake in Yellowstone National Park, five to nine miles south-southeast of Fishing Bridge, Wyoming. The swarm began yesterday afternoon, Dec. 26, and has continued and intensified today. The two largest earthquakes in this swarm have been shocks of magnitude 3.5 and 3.4 which occurred at 1:17 and 1:26 pm MST, respectively, today. Many smaller earthquakes have also occurred, including three events this morning of magnitude 2.5 to 2.8 and a magnitude 3.2 event at 3:30 pm MST. Some of the earthquakes in the swarm have been reported felt by people in the Yellowstone Lake area. Swarms of this nature are relatively common in this part of Yellowstone Park.

These swarms are suggestive of magma movement, but given the nature of Yellowstone Park, that's not saying much. There's lots of magma movement.

What is of interest is if this remains a trend. Sustained swarms, coupled with changing depths of the earthquakes, could suggest a volcano is developing. Right now, there is enough data to say what, if anything, is happening. But it is enough to command some attention.

Further resources:

USGS Yellowstone Volcano Observatory
University of Utah Seismograph Stations
UUSS Recent Earthquakes in Yellowstone


UPDATE, 4:00 PM:

From Breitbart.com:

Scientists watch unusual Yellowstone quake swarm

Scientists are closely monitoring more than 250 small earthquakes that have occurred in Yellowstone National Park since Friday.

Swarms of small earthquakes happen frequently in Yellowstone. But Robert Smith, a professor of geophysics at the University of Utah, says it's very unusual to have so many over several days.

The largest tremor was Saturday and measured magnitude 3.8.

Smith says it's hard to say what might be causing the tremors but notes that Yellowstone is very geologically active. An active volcano there last erupted 70,000 years ago.

Tracing the Wasatch Fault

Courtesy of the Utah Geological Survey: