Category: Volcanic Events


Could Dangerous Underwater Volcano in Caribbean Cause a US Tsunami?

PHOTO: View from "Hercules," a 5,000-pound submersible used by Robert Ballard and his team.
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A team of scientists is exploring the darkest corners of a huge underwater volcano in the Caribbean in hopes of better understanding the mysteries of earthquakes and tsunamis, ultimately saving lives.

Kick’em Jenny is a dangerous and active volcano sitting roughly 6,000 feet below the surface of the Caribbean Sea, and located off the coast of the island of Grenada, south of St. Lucia.

Robert Ballard, famous for discovering the Titanic 12,000 feet below the surface of the icy North Atlantic in 1985, set his sights on exploring the Kick’em Jenny to study its eruption history and learn more about how underwater volcanoes can pose a threat.

Ballard, the president of The Ocean Exploration Trust and the director of the Center for Ocean Exploration at the University of Rhode Island’s Graduate School of Oceanography, said the Kick’em Jenny volcano has a history of explosive eruptions, which could have the potential to trigger tsunamis, the effects from which could be felt as far away as the northeastern United States.

 

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Reuters

Magma rising in Washington state’s Mount St. Helens volcano: USGS

SEATTLE Thu May 1, 2014 3:35pm EDT

Visitors to the Coldwater Ridge Center look up at Mount St. Helens venting steam October 11, 2004. REUTERS/Andy Clark

Visitors to the Coldwater Ridge Center look up at Mount St. Helens venting steam October 11, 2004.

Credit: Reuters/Andy Clark


(Reuters) – Magma levels are slowly rebuilding inside Mount St. Helens, a volcano in Washington state that erupted in 1980 and killed 57 people, although there was no sign of an impending eruption, U.S. scientists said.

The roughly 8,300-foot volcano erupted in an explosion of hot ash and gas on May 18, 1980, spewing debris over some 230 square miles and causing more than a billion dollars in property damage. Entire forests were crushed and river systems altered in the blast, which began with a 5.2 magnitude earthquake.

“The magma reservoir beneath Mount St. Helens has been slowly re-pressurizing since 2008,” the U.S. Geological Survey said in a statement on Wednesday. “It is likely that re-pressurization is caused by (the) arrival of a small amount of additional magma 4 to 8 km (2.5 to 5 miles) beneath the surface.”

Read More Here

 

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Mount St. Helens erupting March 18th, 1980  by  U.S. government

Wikimedia.org

File:Mount St. Helens erupting blue.jpg

U.S. Geological Survey scientist examines pumice blocks at the edge of a pyroclastic flow from the May 18, 1980 eruption.  by  United States Geological Survey  -  Donald A. Swanson

Wikimedia.org

File:Pyroclastic Flow St. Helens.jpg

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Mount Saint Helens, State of Washington, United-States  7 September 2004  by  TjkFlickr

Wikimedia.org

File:Mount St Helens4.jpg

 

 

Crater / Plume image Mount St. Helens. United States Geological Survey photograph taken at 12:13:01 PDT (19:13:01 GMT) on October 1, 2004, by John Pallister

Wikimedia.org

File:MSH04 crater eruption image 1213PDT 10-01-04.jpg

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Mount St. Helens volcano, Washington, USA.  June 7th, 2012  by  Brigitte Werner (werner22brigitte)

Wikimedia.org

File:Mount St Helens USA 20120607.jpg

A panorama of Mount St. Helens  Decenber 18th ,2013  by   Eviatar Bach

Wkimedia.org

File:Panorama of Mount St. Helens.jpg

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Earth Watch Report  -  Volcanic Activity

Evacuations ordered as Peru volcano spews ash 4 km high

Evacuations ordered as Peru volcano spews ash 4 km high

Volcano Eruption Peru Moquegua Region, [Ubinas Volcano] Damage level Details

 

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RSOE EDIS

Volcano Eruption in Peru on Thursday, 17 April, 2014 at 03:28 (03:28 AM) UTC.

Description
The Scientific Permanent Monitoring Committee and the Peruvian have declared Ubinas volcano on orange alert, meaning that local communities have to be evacuated. The volcano, which has been active again since September last year, erupted March 31, giving off ash for one thousand meters. The 20 families living in Querapi were temporarily evacuated shortly after the eruption, but are yet to be permanently relocated to Pampas de Hawái. As well as residents of Querapi, people living in Tonohaya, also in Moquegua, and San Juan de Tarucani, Arequipa, also need to be evacuated. Civil Defense chief, Miguel Alayza said that they were waiting for the alert to go from yellow to the more serious orange before they could proceed. Regional president of Moquegua, Martín Vizcarra said that the volcanic activity would affect five thousand people in that area, while in San Juan de Tarucani, Arequipa, 637 families would be affected, according to El Comercio. Ubinas volcano is considered to be the most active volcano of Peru. Eruptions have been reported since 1550.

 

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RSOE EDIS

Volcano Eruption in Peru on Thursday, 17 April, 2014 at 03:28 (03:28 AM) UTC.

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Updated: Friday, 18 April, 2014 at 04:04 UTC
Description
Peruvian authorities have ordered the preventative evacuation of 4,000 people living near the Ubinas volcano, which has been spouting ash clouds up to 4 kilometres high. The Andina state news agency quotes Agriculture Minister Juan Benites as saying it will take three days beginning today to move the residents of two southern districts and their 30,000 sheep, cows, horses, burros and other animals. Peru’s health ministry says about 40 people have complained of eye inflammation and stomach problems from ash that has been falling from Ubinas since March 29. The 5,672-metre volcano is Peru’s most active. It most recent strong eruption period occurred from 2006-2009.

 

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Evacuations ordered as Peru volcano spews ash 4 km high

Evacuations ordered as Peru volcano spews ash 4 km high

PanARMENIAN.Net – Peruvian authorities have ordered the preventative evacuation of 4,000 people living near the Ubinas volcano, which has been spouting ash clouds up to 2 miles (nearly 4 kilometers) high.

The Andina state news agency quotes Agriculture Minister Juan Benites as saying it will take three days beginning Thursday, April 17, to move the residents of two southern districts and their 30,000 sheep, cows, horses, burros and other animals.

 

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Peru evacuates Ubinas volcano area after ash cloud

Footage shows huge clouds of ash escaping from Ubinas

Officials said it would take three days to move 4,000 residents and their livestock to safer grounds.

Ubinas, Peru’s most active volcano, recently began spewing ash clouds up to 4km (two miles) high.

An eruption of cinder and toxic gases in 2006 killed livestock and forced a similar evacuation.

 

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Earth Watch Report  -  Volcanic Activity

 

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Volcano Eruption Japan Pacific Ocean, [Nishino-Shima volcano, Izu Islands] Damage level Details

 

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Volcano Eruption in Japan on Monday, 07 April, 2014 at 05:25 (05:25 AM) UTC.

Description
The ongoing eruption continues to add new land to the island with what seems a relatively steady effusion of lava flows. A new overflight by the Japanese Coast Guard shows that at least the second vent that appeared in late January is still active, feeding lava flows that continue to spread and currently have active fronts all along the eastern coast. The first original vent (cone 1, right in the picture) that build the new island and grew to a nice, symmetrical cone, seems to be inactive at present. The other vent is still active and has grown a bit since the previous overflight, with a crater that emits an ash and steam plume, presumably from mild explosive activity caused by infiltrating sea water that becomes in contact with the magma. Bluish gas on the pictures shows areas where active lava flows near their vents.
Landsat 8 infrared images from 30 March show that there are active flow fronts all along the eastern coast, while only 2 lobes are active towards the west.

 

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VolcanoDiscovery's start page

Nishino-Shima volcano (Izu Islands, Japan): lava flows continue to enlarge island

Monday Apr 07, 2014 06:24 AM | BY: T

 

Aerial view of Nishinoshima on  24 March 2014 (Japan Coast Guard)

Aerial view of Nishinoshima on 24 March 2014 (Japan Coast Guard)

 

The ongoing eruption continues to add new land to the island with what seems a relatively steady effusion of lava flows. A new overflight by the Japanese Coast Guard shows that at least the second vent that appeared in late January is still active, feeding lava flows that continue to spread and currently have active fronts all along the eastern coast.

 

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VolcanoDiscovery's start page

Nishino-shima volcano (Volcano Islands, Japan) activity update

Part of Nishino-shima island with active flows on the southern shore, forming new bays and a small lake that once was a bay (Japan Coast guard)
Tuesday, Mar 04, 2014
The island continues to grow as lava flows slowly spread into several directions. This is shown nicely by the latest aerial survey pictures the Japanese Coast guard took on 28 Feb. The most active flow fronts are currently at the southern shore while advance on the northern and eastern margins of the flow field has slowed down. … [more]

 

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Earth Watch Report  -  Volcanic Activity

 

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RSOE EDIS

Volcano Eruption Ecuador Andes, [Reventador volcano] Damage level Details

 

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Volcano Eruption in Ecuador on Thursday, 27 March, 2014 at 04:08 (04:08 AM) UTC.

Description
The volcano has entered a new eruptive phase since yesterday, Ecuador’s Institute of Geophysics (IGP) reported. Starting from 15:00 local time yesterday, increasing tremor was registered and steady ash emissions were observed. At night, incandescent blocks could be seen and heard rolling down from the crater where probably a new lava dome has started to appear. Small pyroclastic flows descended on the eastern, southeastern and southern flanks of the volcano, probably as a result of re-mobilization of fresh lava and tephra deposits. These so-called secondary pyroclastic flows reached lengths of 500 m below the summit. IGP assumes the most likely scenario for the evolution of the new eruptive episode is that activity continues at similar levels for a while. So far, lava avalanches and pyroclastic flows have been confined within the caldera, near the flanks of the main cone. So far, no reports of ash falls became available from communities in the nearby areas, suggesting that the eruption is still small. An important hazard remains in the form of lahars (mud flows), which can be generated by re-mobilization of loose material during heavy rainfall and would most likely threaten the bed and banks of the Quijo river.

 

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VolcanoDiscovery's start page

Reventador volcano, Ecuador: news & activity updates

Reventador volcano (Ecuador): new eruption

Wednesday Mar 26, 2014 16:36 PM | BY: T

Continuous ash emission and incandescent avalanches on Reventador's eastern flank (image: G. Taipe / IGP)

Continuous ash emission and incandescent avalanches on Reventador’s eastern flank (image: G. Taipe / IGP)

… IGP assumes the most likely scenario for the evolution of the new eruptive episode is that activity continues at similar levels for a while. So far, lava avalanches and pyroclastic flows have been confined within the caldera, near the flanks of the main cone. So far, no reports of ash falls became available from communities in the nearby areas, suggesting that the eruption is still small. An important hazard remains in the form of lahars (mud flows), which can be generated by re-mobilization of loose material during heavy rainfall and would most likely threaten the bed and banks of the Quijo river.

 

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LiveScience

Iceland’s Hekla Volcano Close to Erupting, Scientist Claims

  

Earth from Space Iceland 1000
This Envisat image shows us a very rare, cloud-free view of Iceland. This image was acquired on July 21, 2010.
Credit: ESA

Hekla volcano, one of Iceland’s most active volcanoes, could be close to erupting, a University of Iceland geoscientist claims.

The most prominent sign of an impending eruption is bulging ground on the northern side of the volcano. This surface swelling indicates magma (molten rock) is rising under the volcano, pushing up the ground as it fills fractures and pipes beneath Hekla. According to GPS monitoring of the expanding surface, there is now more magma underneath Hekla than before the volcano’s last eruption in 2000, University of Iceland geophysicist Páll Einarsson said in a report published in the Icelandic newspaper Morgunblaðið on Monday (March 17). Hekla volcano “could erupt soon,” Einarsson said.

 

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Earth Watch Report   -  Volcanic Actuivity

Copahue volcano, quiet at the surface, today (SERNAGEOMIN webcam)

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Volcano Activity MultiCountries Argentina and Chile (Andes), [Copahue Volcano] Damage level Details

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RSOE EDIS

Volcano Activity in MultiCountries on Saturday, 22 March, 2014 at 05:22 (05:22 AM) UTC.

Description
SERNAGEOMIN raised the alert level of the volcano to orange yesterday after an increase in seismic activity. A pulse of volcanic tremor was detected that could indicate magma moving into the volcano’s plumbing system. On the surface, no unusual activity has been seen at the volcano so far, except that an increase in SO2 emissions (approx 2,300 tons / day) was measured. This supports the idea that magma has risen under the edifice. Whether this activity is followed by new eruptive activity remains to be seen. In most cases, intrusions of magma under volcanoes do never reach the surface, i.e. produce eruptions. ONEMI (Civil Defense) published a bulletin stating that civil alert remains at yellow for the highest risk areas, in particular the most proximal areas around the volcano itself, but also include the city of Alto Biobío located 40 km west of the volcano, because it is at the mouth of a valley that drains Copahue on the north side and therefore, a potential pathway for mud flows that could occur during an eruption.

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Volcano Discovery

Copahue volcano

stratovolcano 2997 m / 9,833 ft
Chile/Argentina, -37.85°S / -71.17°W

Copahue webcams / live data
Copahue volcano videos
Copahue volcano eruptions:
2013, 2012, 2001(?), 2000, 1992, 1961, 1937, 1867(?), 1759(?), 1750
Typical eruption style:
explosive
Last earthquakes nearby

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Wednesday, Mar 12, 2014
The volcano continues to show signs of unrest. A swarm of volcanic-tectonic earthquakes occurred the day before yesterday. SERNAGEOMIN keeps the alert level of the volcano at Yellow. [more]

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Earth Watch Report  -  Volcanic Activity

mount of slamet

mount of slamet

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Volcano Eruption Indonesia West Java, [Slamet volcano] Damage level Details

 

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RSOE EDIS

Volcano Eruption in Indonesia on Tuesday, 11 March, 2014 at 11:06 (11:06 AM) UTC.

Description
New eruptions were observed at Java’s second highest volcano since yesterday evening. A series of explosions produced ash plumes rising 800-1000 m above the summit, the local observatory reported. This activity came after a steep increase in volcanic earthquakes from averages of approx 50 to more than 200 per day, volcanologist Mr Sudrajat from the local observatory told the press. The first explosion occurred Monday evening at 20:06, causing the glass windows of the observatory building to vibrate. Shortly after, the Center for Volcanology and Geological Hazard Mitigation (PVMBG) raised the status of Mount Slamet from normal to alert (2 on a scale of 1-4). According to local press, the vibration from the eruption could be felt in up to 10 km distance and described the plume as “thick smoke”. Slamet is one of Java’s most active volcanoes and often has strombolian to vulcanian-type activity in its summit crater.

 

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Volcano Hiking Routes Closed as Mount Slamet Put on Alert in Central Java

By Jakarta Globe on 01:32 pm Mar 11, 2014

Jakarta/Purbalingga. Indonesia’s geological agency sounded an alert for the Central Java volcano Mount Slamet on Tuesday, advising hikers to avoid the crater rim but falling short of instructing local communities to evacuate.

“It started on Monday evening at 9 p.m,” said Sutopo Purwo Nugroho, head of the National Disaster Response Agency (BNPB), in a text message sent on Tuesday.

The Center of Volcanic and Geological Disaster Mitigation (PVMBG) raised the status of Mount Slamet in Central Java activity to the second level of alert: waspada.

Sutopo said volcanic activity was a potential risk for five sub-districts located around Mount Slamet: Banyumas, Brebes, Pembalang, Purbalingga and Tegal.

The PVMBG has recorded 441 minor quakes and 9 shallow volcanic quakes since March 8.

“We suggest residents stay calm and not panic,” Sutopo said. ”We also recommend tourists, hikers and residents do not to hike the mountain or do anything within the two-kilometer radius of Mount Slamet’s crater.”

The Regional Disaster Mitigation Agency (BPBD) has not warned residents directly.

“We have not officially warned the people living in around Mount Slamet, especially the ones in Purbalingga sub-district, like Kutabawa village, Karangreja ward, and others,” Purbalingga BPBD chief Priyo Satmoko said on Tueday.

 

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Earth Watch Report  -  Volcanic Events

File:Merapi ash plume MODIS sat image 10 Nov 2010.jpg

Thick plume of ash rising from the Merapi Volcano on November 10, 2010 and travelling to the west. From Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite, A dark brown streak down the southern face of the volcano is ash and other volcanic material deposited by a pyroclastic flow or lahar.

Author  –   NASA  public domain

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February 26 2014 05:34 PM Volcano Activity Indonesia West Sumatra, [Mount Merapi Volcano] Damage level Details

 

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Volcano Activity in Indonesia on Wednesday, 26 February, 2014 at 17:34 (05:34 PM) UTC.

 

Description
Another ash eruption occurred at the volcano this afternoon at 16:15 local time. According to local news quoting the local VSI volcano observatory spokesman, the eruption today was the largest in a series since the alert status had been raised on 3 August last year. Ash fell in a radius of 3 km where some villages are located. Also according to the article, the volcano has had a total of 57 recorded eruptions since January 2014. Since all of these have been small, and Indonesia is very used to small volcanic eruptions, they hardly make any news at all (while such an event at other volcanoes would). The alert status remains unchanged at 2 out of 4. People were recommended to avoid exposure to ash if possible and wear dust masks.

 

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Metro TV News

The Citizens Of Merapi Prompted To Be Alert

Kamis, 13 February 2014 | 15:10 WIB

ANTARA/Noveradika/ip
Metrotvnews.com, Klaten district: citizens around Merapi are asked to remain vigilant of  activity. In the meantime, residents have asked that the damaged to evacuation routes on the slopes of  the Mount  be repaired immediately.
Citizens are urged  to take precautions against disasters , the volcano’s activity in some areas has increased  of late.
“Despite the conditions,  the mountain looks to still be active,  citizens who live in KRB III Merapi should remain vigilant. As the anticipated  eruptions could occur at any time, “is explained to the Indonesian Media .
The number of residents at KRB III Merapi, according to Joko,  are about 5,700 inhabitants. They are scattered throughout a number of villages in the subdistrict of Kemalang, among them  the villages of Sidorejo, Balerante, Tegalmulyo..
The government   has set up three refugee shelters in case of eruption .  Each of which has a capacity of about 2,000 people.  The  centers built  by BNPB are located in Prambanan, Karangnongko, and Kebonarum.
In the meantime, Sukamto, a 50 year old socialite in Balerante Village, has asked that the Government   repair a damaged evacuation path on the slope of Merapi.   Repairs would make for a smooth evacuation and ensure security if the mountain erupted.
In addition, the bridge that was badly damaged on the evacuation route also needs to be repaired.
Editor: Henri Solomon Siagian

 

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Merapi volcano (Sumatra, Indonesia): new ash explosions

 

Wednesday Feb 26, 2014 17:41 PM | BY: T

Another ash eruption occurred at the volcano this afternoon at 16:15 local time. According to local news quoting the local VSI volcano observatory spokesman, the eruption today was the largest in a series since the alert status had been raised on 3 August last year.

 

Read More Here

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Earth Watch Report  -  Earthquakes

M4.5 – 10km NNW of Banqiao, Taiwan 2014-02-11 16:31:03 UTC

Earthquake location 25.105°N, 121.434°E

A map shows the epicenter, top, in red, of the magnitude 4 earthquake that hit Taipei’s Shilin District at 12:31am yesterday.

Photo courtesy of National Taiwan University professor Chen Hung-yu

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February 12 2014 05:39 PM Earthquake Taiwan Shilin District, [Tatun Volcano Group] Damage level Details

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Earthquake in Taiwan on Wednesday, 12 February, 2014 at 17:39 (05:39 PM) UTC.

Description
Northern Taiwan was rocked by a magnitude 4 earthquake at 12:31am yesterday, renewing concerns about the potential for volcanoes in the Tatun Volcano Group in Yangmingshan National Park to erupt. At press time, no casualties had been reported from the quake and only minor damage – to the Pingdeng Elementary School on Yangmingshan �” was reported. Many residents in the area were startled by the quake, which caused a loud rumbling sound. Central Weather Bureau data showed that the epicenter of the quake was in Taipei’s Shilin District , 11.8km north of Taipei City Hall at a depth of 6.3km. The strongest intensity of the quake, Level 4, was detected on Yangmingshan, followed by Level 3 in Wugu in New Taipei City and Taoyuan City, and Level 2 in Taipei and Keelung. The bureau’s records show that 19 earthquakes with a magnitude exceeding 3 have occurred within a 5km radius of the epicenter of yesterday’s quake since 1980. The largest one was in 1988, with a magnitude of 5.3. Yesterday’s quake was the strongest within the perimeter of the Tatun group in 26 years, the bureau said. Seismology Center Director Kuo Kai-wen said the earthquake was a stress adjustment that occurs after lava cools down. “When the lava in a volcano cools down, it shrinks in size. This will subsequently lead to gaps in the rock layers. Pulled by gravity, the rock layer on top falls. This kind of stress adjustment is quite normal,” he said. Yesterday’s quake was not caused by the active fault at the foot of Yangminshan, as its epicenter and the fault are about 6km apart, Kuo said. Nevertheless, the earthquake generated concern that one or more of the Tatun volcanoes might erupt soon. Kuo said that was an unlikely scenario. “The volcanoes in Tatun are generally considered dormant. Currently, only three to five small earthquakes happen in the area per day. On average, the volcanoes could erupt if there are more than 100 to 200 earthquakes per day, and they have to escalate from deep earthquakes to shallow earthquakes,” he said. However, National Taiwan University professor Chen Hongey said the government needs to carefully examine the correlations between yesterday’s magnitude 4 earthquake and the active fault, adding that it was quite unusual for an earthquake to occur at the volcanic zone.

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Event Time

  1. 2014-02-11 16:31:03 UTC
  2. 2014-02-12 00:31:03 UTC+08:00 at epicenter
  3. 2014-02-11 10:31:03 UTC-06:00 system time

Location

25.105°N 121.434°E depth=14.0km (8.7mi)

Nearby Cities

  1. 10km (6mi) NNW of Banqiao, Taiwan
  2. 11km (7mi) WNW of Taipei, Taiwan
  3. 18km (11mi) NE of Taoyuan City, Taiwan
  4. 28km (17mi) NNE of Daxi, Taiwan
  5. 804km (500mi) ENE of Hong Kong, Hong Kong

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Tectonic Summary

Seismotectonics of the Philippine Sea and Vicinity

The Philippine Sea plate is bordered by the larger Pacific and Eurasia plates and the smaller Sunda plate. The Philippine Sea plate is unusual in that its borders are nearly all zones of plate convergence. The Pacific plate is subducted into the mantle, south of Japan, beneath the Izu-Bonin and Mariana island arcs, which extend more than 3,000 km along the eastern margin of the Philippine Sea plate. This subduction zone is characterized by rapid plate convergence and high-level seismicity extending to depths of over 600 km. In spite of this extensive zone of plate convergence, the plate interface has been associated with few great (M>8.0) ‘megathrust’ earthquakes. This low seismic energy release is thought to result from weak coupling along the plate interface (Scholz and Campos, 1995). These convergent plate margins are also associated with unusual zones of back-arc extension (along with resulting seismic activity) that decouple the volcanic island arcs from the remainder of the Philippine Sea Plate (Karig et al., 1978; Klaus et al., 1992).

South of the Mariana arc, the Pacific plate is subducted beneath the Yap Islands along the Yap trench. The long zone of Pacific plate subduction at the eastern margin of the Philippine Sea Plate is responsible for the generation of the deep Izu-Bonin, Mariana, and Yap trenches as well as parallel chains of islands and volcanoes, typical of circum-pacific island arcs. Similarly, the northwestern margin of the Philippine Sea plate is subducting beneath the Eurasia plate along a convergent zone, extending from southern Honshu to the northeastern coast of Taiwan, manifested by the Ryukyu Islands and the Nansei-Shoto (Ryukyu) trench. The Ryukyu Subduction Zone is associated with a similar zone of back-arc extension, the Okinawa Trough. At Taiwan, the plate boundary is characterized by a zone of arc-continent collision, whereby the northern end of the Luzon island arc is colliding with the buoyant crust of the Eurasia continental margin offshore China.

Along its western margin, the Philippine Sea plate is associated with a zone of oblique convergence with the Sunda Plate. This highly active convergent plate boundary extends along both sides the Philippine Islands, from Luzon in the north to the Celebes Islands in the south. The tectonic setting of the Philippines is unusual in several respects: it is characterized by opposite-facing subduction systems on its east and west sides; the archipelago is cut by a major transform fault, the Philippine Fault; and the arc complex itself is marked by active volcanism, faulting, and high seismic activity. Subduction of the Philippine Sea Plate occurs at the eastern margin of the archipelago along the Philippine Trench and its northern extension, the East Luzon Trough. The East Luzon Trough is thought to be an unusual example of a subduction zone in the process of formation, as the Philippine Trench system gradually extends northward (Hamburger et al., 1983). On the west side of Luzon, the Sunda Plate subducts eastward along a series of trenches, including the Manila Trench in the north, the smaller less well-developed Negros Trench in the central Philippines, and the Sulu and Cotabato trenches in the south (Cardwell et al., 1980). At its northern and southern terminations, subduction at the Manila Trench is interrupted by arc-continent collision, between the northern Philippine arc and the Eurasian continental margin at Taiwan and between the Sulu-Borneo Block and Luzon at the island of Mindoro. The Philippine fault, which extends over 1,200 km within the Philippine arc, is seismically active. The fault has been associated with major historical earthquakes, including the destructive M7.6 Luzon earthquake of 1990 (Yoshida and Abe, 1992). A number of other active intra-arc fault systems are associated with high seismic activity, including the Cotabato Fault and the Verde Passage-Sibuyan Sea Fault (Galgana et al., 2007).

Relative plate motion vectors near the Philippines (about 80 mm/yr) is oblique to the plate boundary along the two plate margins of central Luzon, where it is partitioned into orthogonal plate convergence along the trenches and nearly pure translational motion along the Philippine Fault (Barrier et al., 1991). Profiles B and C reveal evidence of opposing inclined seismic zones at intermediate depths (roughly 70-300 km) and complex tectonics at the surface along the Philippine Fault.

Several relevant tectonic elements, plate boundaries and active volcanoes, provide a context for the seismicity presented on the main map. The plate boundaries are most accurate along the axis of the trenches and more diffuse or speculative in the South China Sea and Lesser Sunda Islands. The active volcanic arcs (Siebert and Simkin, 2002) follow the Izu, Volcano, Mariana, and Ryukyu island chains and the main Philippine islands parallel to the Manila, Negros, Cotabato, and Philippine trenches.

Seismic activity along the boundaries of the Philippine Sea Plate (Allen et al., 2009) has produced 7 great (M>8.0) earthquakes and 250 large (M>7) events. Among the most destructive events were the 1923 Kanto, the 1948 Fukui and the 1995 Kobe (Japan) earthquakes (99,000, 5,100, and 6,400 casualties, respectively), the 1935 and the 1999 Chi-Chi (Taiwan) earthquakes (3,300 and 2,500 casualties, respectively), and the 1976 M7.6 Moro Gulf and 1990 M7.6 Luzon (Philippines) earthquakes (7,100 and 2,400 casualties, respectively). There have also been a number of tsunami-generating events in the region, including the Moro Gulf earthquake, whose tsunami resulted in more than 5000 deaths.

More information on regional seismicity and tectonics

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Shilin earthquake renews concern about volcanoes

YANGMINGSHAN PARK:The Central Weather Bureau said the 12:31am quake was the largest one within the perimeters of the Tatun Volcano Group in 26 years

By Shelley Shan  /  Staff reporter

A map shows the epicenter, top, in red, of the magnitude 4 earthquake that hit Taipei’s Shilin District at 12:31am yesterday.

Photo courtesy of National Taiwan University professor Chen Hung-yu

Northern Taiwan was rocked by a magnitude 4 earthquake at 12:31am yesterday, renewing concerns about the potential for volcanoes in the Tatun Volcano Group (大屯火山群) in Yangmingshan National Park to erupt.

At press time, no casualties had been reported from the quake and only minor damage — to the Pingdeng Elementary School on Yangmingshan — was reported.

Many residents in the area were startled by the quake, which caused a loud rumbling sound.

Central Weather Bureau data showed that the epicenter of the quake was in Taipei’s Shilin District (士林), 11.8km north of Taipei City Hall at a depth of 6.3km.

The strongest intensity of the quake, Level 4, was detected on Yangmingshan, followed by Level 3 in Wugu (五股) in New Taipei City (新北市) and Taoyuan City, and Level 2 in Taipei and Keelung.

The bureau’s records show that 19 earthquakes with a magnitude exceeding 3 have occurred within a 5km radius of the epicenter of yesterday’s quake since 1980. The largest one was in 1988, with a magnitude of 5.3.

Read More Here

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