Earth Watch Report – Friday August 31st, 2012

August 31, 2012 by desertrose

LISS – Live Internet Seismic Server

GSN Stations

These data update automatically every 30 minutes. Last update: August 31, 2012 08:19:06 UTC

Seismograms may take several moments to load. Click on a plot to see larger image.

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Volcanic Activity

Earthquakes raise alert level at Alaska volcano

Related

• Alaska’s biggest volcanic eruptions
• (Update) Iliamna volcano: ‘Seismic swarm’, but eruption not likely

A series of small earthquakes which began Wednesday night and continued into Thursday near a long-dormant volcanic peak in Alaska’s Aleutian Islands has prompted researchers to raise the alert level for the Little Sitkin volcano.

The nearly 4,000-foot-high Little Sitkin volcano is named for the island where it resides, located in the Rat Islands in the Aleutian chain. The volcano has shown little activity since scientists have started observing it, with only three questionable eruptive events at the volcano since that time. The most recent eruption may have come in 1900, according to the Alaska Volcano Observatory.

Still, the AVO page for Little Sitkin mentions there may have been a “cataclysmic eruption” on the island sometime after the last ice age, which ended more than 11,000 years ago.

Seismic equipment located near the volcano began detecting a “swarm of high-frequency earthquakes” at about 7:15 p.m. Wednesday, the AVO reports. The earthquakes continued through the night into Thursday, prompting the alert level at the volcano being raised. The alert level is currently at yellow, which means that the “volcano is exhibiting signs of elevated unrest above known background level.” Additionally, aircraft traveling in the area are advised to exercise caution.

The volcano is located in a remote part of the Aleutians, about 35 miles northwest of the World War II outpost of Amchitka and 200 miles west of Adak.

Little Sitkin joins two other Alaska volcanoes, Iliamna and Cleveland, currently sitting at elevated alert levels.

Photos: Alaska volcanoes

Apr 02, 2012

Pavlof volcano and eruption plume on evening of Aug. 30, 2007. View is to the south. Plume height approximately 17-18,000 ft.

Chris Waythomas/Alaska Volcano Observatory photo

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Iliamna, 130 miles from Anchorage, Alaska’s largest city, was first elevated in March of this year following a continued increase in seismic activity.

“The current level of activity at Iliamna does not indicate an imminent or certain eruption,” a status update from the AVO said Thursday. “Seismic activity, along with gas emissions, appear to be declining gradually.”

Meanwhile, the oft-erupting Cleveland volcano which, like Sitkin, is located in the Aleutians, remains elevated as well. Cleveland has been upgraded a half-dozen times in since 2010 alone, and most recently erupted in June, when a pilot reported an ash cloud reaching up to 35,000 feet. Cleveland sits at a higher alert level than Iliamna or Little Sitkin, meaning the volcano still has a higher potential for eruption at any time.

For updates on these and other volcanoes across Alaska, visit the Alaska Volcano Observatory.

Contact Ben Anderson at ben(at)alaskadispatch.com

Today

Volcano Activity

USA

State of Alaska, [Little Sitkin Volcano]

Volcano Activity in USA on Friday, 31 August, 2012 at 02:27 (02:27 AM) UTC.

Earth Watch Report – Saturday August 25th, 2012

August 25, 2012 by desertrose 

Earthquakes

RSOE EDIS

Date/Time (UTC)	Magnitude	Area	Country	State/Prov./Gov.	Location	Risk			Source	Details
25.08.2012 10:45:36	2.9	North America	United States	California	Cobb				USGS-RSOE
25.08.2012 10:50:23	2.3	Europe	Italy	Calabria	Salerni				EMSC
25.08.2012 10:35:34	2.1	North America	United States	Alaska	Sterling				USGS-RSOE
25.08.2012 10:50:47	2.4	Europe	Italy	Calabria	Salerni				EMSC
25.08.2012 10:40:33	3.4	Caribbean	British Virgin Islands		Road Town				USGS-RSOE
25.08.2012 09:50:19	4.1	Asia	Turkey	Manisa	Golmarmara				EMSC
25.08.2012 09:20:57	2.3	North America	United States	California	Big Bear Lake				USGS-RSOE
25.08.2012 10:00:30	4.0	Caribbean	British Virgin Islands		Road Town				USGS-RSOE
25.08.2012 10:51:10	4.0	Caribbean Sea	British Virgin Islands		Road Town				EMSC
25.08.2012 10:52:02	3.9	Caribbean	British Virgin Islands		Road Town				USGS-RSOE
25.08.2012 08:52:29	2.3	North America	United States	California	Saratoga				USGS-RSOE
25.08.2012 08:30:56	2.8	North America	United States	Utah	Big Water				USGS-RSOE
25.08.2012 08:50:20	3.8	Europe	Greece	Central Greece	Roviai				EMSC
25.08.2012 08:50:51	2.9	Europe	Greece	Crete	Kissamos				EMSC
25.08.2012 08:51:34	2.4	Europe	Bosnia and Herzegovina	Federation of Bosnia and Herzegovina	Vitez				EMSC
25.08.2012 07:50:18	2.4	Europe	Greece	North Aegean	Mithymna				EMSC
25.08.2012 06:45:26	3.1	South-America	Chile	Región Metropolitana	La Pintana				EMSC
25.08.2012 05:55:33	2.8	North America	United States	California	Avalon				USGS-RSOE
25.08.2012 07:50:43	2.3	Asia	Turkey	Amasya	Dedekoy				EMSC
25.08.2012 07:51:04	3.8	Europe	Russia	Tyva	Sukpak				EMSC
25.08.2012 07:51:25	2.6	Asia	Turkey	Antalya	Kalkan				EMSC
25.08.2012 05:50:28	4.4	Pacific Ocean – West	Vanuatu	Torba	Sola				USGS-RSOE
25.08.2012 06:45:45	4.4	Pacific Ocean – West	Vanuatu	Torba	Sola				EMSC
25.08.2012 06:46:03	2.8	Asia	Turkey	Amasya	Dedekoy				EMSC
25.08.2012 05:40:37	2.8	Asia	Turkey	Amasya	Dedekoy				EMSC
25.08.2012 06:46:22	2.2	Asia	Turkey	Amasya	Dedekoy				EMSC
25.08.2012 04:56:05	2.5	North America	United States	California	Indianola				USGS-RSOE
25.08.2012 05:41:44	3.1	Europe	Greece	Crete	Yialos				EMSC
25.08.2012 04:40:50	2.3	North America	United States	Alaska	Petersville				USGS-RSOE
25.08.2012 04:40:21	2.5	Europe	Italy	Sicily	Saponara Villafranca				EMSC
25.08.2012 03:40:20	2.7	Europe	Romania	Mehedin?i	Svinita				EMSC
25.08.2012 03:40:44	3.5	Europe	Greece	Peloponnese	Elafonisos				EMSC
25.08.2012 02:45:55	3.1	Caribbean	U.S. Virgin Islands	Saint Thomas Island	Charlotte Amalie				USGS-RSOE
25.08.2012 03:41:10	4.1	Africa	Algeria	Chlef	Sidi Akkacha				EMSC
25.08.2012 01:16:21	2.1	North America	United States	California	Big Bear City				USGS-RSOE
25.08.2012 06:16:00	2.2	North America	United States	Oregon	Paisley				USGS-RSOE
25.08.2012 01:40:18	4.6	Indonesian Archipelago	Indonesia	Bengkulu	Curup				EMSC
25.08.2012 01:41:38	4.7	Indonesian archipelago	Indonesia	Bengkulu	Curup				USGS-RSOE
25.08.2012 01:40:46	2.4	Europe	Italy	Calabria	Nicastro				EMSC
25.08.2012 01:41:11	4.4	South-America	Chile	Valparaíso	San Antonio				EMSC
25.08.2012 00:50:57	4.7	South America	Chile	Valparaíso	San Antonio				USGS-RSOE
25.08.2012 00:35:26	2.4	Europe	Italy	Abruzzo	Balsorano Vecchio				EMSC
25.08.2012 00:35:51	3.0	Europe	Greece	North Aegean	Agia Paraskevi				EMSC
25.08.2012 00:36:13	2.0	Europe	Italy	Lombardy	Ospitaletto				EMSC
25.08.2012 00:05:27	3.9	North America	United States	Alaska	Healy				USGS-RSOE
25.08.2012 00:36:34	4.7	Indonesian Archipelago	Indonesia	Aceh	Meulaboh				EMSC
25.08.2012 00:10:26	4.7	Indonesian archipelago	Indonesia	Aceh	Meulaboh				USGS-RSOE
25.08.2012 00:36:55	2.6	Europe	Italy	Emilia-Romagna	San Prospero				EMSC
25.08.2012 06:46:42	2.0	Asia	Turkey	Van	Toyga				EMSC
25.08.2012 00:37:17	2.7	Asia	Turkey	Afyonkarahisar	Kiziloren				EMSC

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Four quakes rock Nepal in past 12 hours

KESHAV P. KOIRALA

KATHMANDU: Four consecutive earthquakes — two of them powerful ones — rocked western Nepal in past 12 hours.

With their epicentres in the border area of Rolpa and Rukum districts, the tremors of the first quake were felt in Kathmandu at 10:15 pm last night.

Its magnitude was 5.6 on the Richter Scale, according to Dilli Ram Tiwari, survey officer at National Seismological Centre (NSC) in Kathmandu.

The second quake was measured at 10:27 pm yesterday, and it was 4.4 in magnitude.

The NSC has recorded two earthquakes this morning also.

The quakes at 6:02 am and 9.40 am were 4.4 and 5.2 on the Richter Scale, Tiwari said.

It is yet to learn whether the quakes caused any damage in the areas near epicentre.

Courtesy: National Seismological Centre, Lainchaur

Antarctic Ice Sheet Quakes Shed Light On Ice Movement and Earthquakes

ScienceDaily

Analysis of small, repeating earthquakes in an Antarctic ice sheet may not only lead to an understanding of glacial movement, but may also shed light on stick slip earthquakes like those on the San Andreas fault or in Haiti, according to Penn State geoscientists.

“No one has ever seen anything with such regularity,” said Lucas K. Zoet, recent Penn State Ph. D. recipient, now a postdoctoral fellow at Iowa State University. “An earthquake every 25 minutes for a year.”

The researchers looked at seismic activity recorded during the Transantarctic Mountains Seismic Experiment from 2002 to 2003 on the David Glacier in Antarctica, coupled with data from the Global Seismic Network station Vanda. They found that the local earthquakes on the David Glacier, about 20,000 identified, were predominantly the same and occurred every 25 minutes give or take five minutes.

The researchers note in the current Nature Geoscience that, “The remarkable similarity of the waveforms … indicates that they share the same source location and source mechanisms.” They suggest that “the same subglacial asperity repeatedly ruptures in response to steady loading from the overlying ice, which is modulated by stress from the tide at the glacier front.”

“Our leading idea is that part of the bedrock is poking through the ductile till layer beneath the glacier,” said Zoet.

The researchers have determined that the asperity — or hill — is about a half mile in diameter.

The glacier, passing over the hill, creates a stick slip situation much like that on the San Andreas fault. The ice sticks on the hill and stress gradually builds until the energy behind the obstruction is high enough to move the ice forward. The ice moves in a step-by-step manner rather than smoothly.

But motion toward the sea is not the only thing acting on the ice streaming from David glacier. Like most glaciers near oceans, the edge of the ice floats out over the water and the floating ice is subject to the action of tides.

“When the tide comes in it pushes back on the ice, making the time between slips slightly longer,” said Sridhar Anandakrishnan, professor of geoscience. “When the tide goes out, the time between slips decreases.”

However, the researchers note that the tides are acting at the ground line, a long way from the location of the asperity and therefore the effects that shorten or lengthen the stick slip cycle are delayed.

“This was something we didn’t expect to see,” said Richard B. Alley, Evan Pugh Professor of Geosciences. “Seeing it is making us reevaluate the basics.”

He also noted that these glacial earthquakes, besides helping glaciologists understand the way ice moves, can provide a simple model for the stick slip earthquakes that occur between landmasses.

“We have not completely explained how ice sheets flow unless we can reproduce this effect,” said Alley. “We can use this as a probe and look into the physics so we better understand how glaciers move.”

Before 2002, this area of the David glacier flowed smoothly, but then for nearly a year the 20-minute earthquake intervals occurred and then stopped. Something occurred at the base of the ice to start and then stop these earthquakes.

“The best idea we have is that during those 300 days, a dirty patch of ice was in contact with the mount, changing the way stress was transferred,” said Zoet. “The glacier is experiencing earthquakes again, although at a different rate. It would be nice to study that.”

Unfortunately, the seismographic instruments that were on the glacier in 2002 no longer exist, and information is coming from only one source at the moment.

Tectonic Shoving Match Formed Caribbean Island Arc

OurAmazingPlanet Staff

The image shows how the Caribbean plate is pushed to the east relative to the South American plate, causing the Caribbean Islands’ distinctive arc shape. CREDIT: Courtesy of Meghan Miller and Thorsten Becker View full size image

The movement of Earth’s viscous mantle against South America has pushed the Caribbean islands east over the last 50 million years, according to a study published Monday (Aug. 20) in the journal Nature Geoscience.

The University of Southern California, in announcing the study, said the findings upend previous hypotheses of the seismic activity beneath the Caribbean Sea and provide an important new look at the unique tectonic interactions that are causing the Caribbean plate to tear away from South America.

The Caribbean plate is being pushed eastward due to a thick section of the South American plate called a “cratonic keel.” This section of crust is three times

Meanwhile, part of the South American plate is being pushed beneath the Caribbean plate, a process called subduction. Intense heat and pressure gradually force water-containing magma to rise into the Earth’s mantle and fuel the many active volcanoes in the region.

All of this pushing and pulling formed the distinctive arc shape of the Caribbean islands and has created a very complex system of faults between the two plates, in northern South America, according to the USC statement. The study mapped several of these strike-slip faults, which are similar to California’s San Andreas Fault.

Recent earthquakes in the area helped the two researchers develop an image of the Earth’s deep interior. The earthquake waves move slower or quicker depending on the temperature and composition of the rock.

“Studying the deep earth interior provides insights into how the Earth has evolved into its present form,” researcher Meghan S. Miller said in the statement.

For their study, the researchers used earthquake data to develop 176 computer models, USC said

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Volcanic Activity

Volcano activity of August 23-24, 2012 – Mt. Tongariro, Sotara, Shiveluch, Karymsky, Santiaguito, Fuego, Sakurajima, Batu Tara, Tungurahua, Kilauea and Nevado del Ruiz

By Richard Wilson and Armand Vervaeck

August , 2012 volcano activity

Mount Tongariro volcano (New Zealand) showed some seismicity earlier today (see seismogram below). The activity can only be seen in Oturere and West Tongariro seismograms (close to the Te Maari craters). Below also one of the rara clear view images of Mt. Tongariro with a strongly steaming vent. N report from GNS science about the seismicity however.  The Park service has announced that the trekking trails at Mount Tongariro would be reopened. A 3 km hazard and risk zone will remain in place for some time and might be further reduced once new information of the gas and ash composition is known.

According to INGEOMINAS, the Observatorio Vulcanológico and Sismológico de Popayán reported that during 8-14 August seismic activity at Sotará increased. The seismic network recorded 110 magnitude 0.2-1.6 events mainly located in an area 0.1-5 km NE of the peak, at depths of 2-6 km. Inflation was detected in the NE area, coincident with the zone of increased seismicity. Web-camera views showed no morphological changes. The Alert Level was raised to III (Yellow; “changes in the behavior of volcanic activity”), or the second lowest level. (Smithsonian Institute)

KVERT reported moderate seismic activity from Karymsky during 10-20 August. Satellite imagery showed a weak thermal anomaly on the volcano during 10-13, 15, and 18-20 August. The Aviation Color Code remained at Orange.

KVERT reported that during 10-18 August weak seismic activity was detected at Shiveluch. Observers noted gas-and-steam activity during 15-17 August; weather conditions prevented observations of the volcano on the other days. Satellite imagery showed a thermal anomaly on the lava dome during 10, 12-13, and 18-19 August. Seismic activity increased to moderate levels and hot avalanches were observed during 19-20 August. The Aviation Color Code remained at Orange.

Insivumeh reports 2 moderate explosions at Santiaguito (Santa Maria), Guatemala. The other Guatemala volcano, Fuego sends a white plume approx. 50 meter in the air and grumbles every 1 to 3 minutes. See also seismograms from both volcanoes.

Activity observed by satellites
VAAC reports still the same volcanoes which can be dangerous for aviation ; Sakurajima, Batu Tara and a very active Tungurahua

SO2 satellite imagery shows SO2 clouds at the following volcanoes : Etna, Kilauea and Nevado del Ruiz. Clouds of a number of other volcanoes are not defined enough to be sure.

A smoking Nevado del Ruiz yesterday – image courtesy Ingeominas Colombia

Earth Watch Report – Sunday August 26th, 2012

August 26, 2012 by desertrose