Earth Watch Report - Earthquakes
M4.5 - 10km NNW of Banqiao, Taiwan 2014-02-11 16:31:03 UTC
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
| February 12 2014 05:39 PM | Earthquake | Taiwan | Shilin District, [Tatun Volcano Group] |  |  |
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. |
Event Time
- 2014-02-11 16:31:03 UTC
- 2014-02-12 00:31:03 UTC+08:00 at epicenter
- 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
- 10km (6mi) NNW of Banqiao, Taiwan
- 11km (7mi) WNW of Taipei, Taiwan
- 18km (11mi) NE of Taoyuan City, Taiwan
- 28km (17mi) NNE of Daxi, Taiwan
- 804km (500mi) ENE of Hong Kong, Hong Kong
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
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
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.
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