|
1879 Surigao Earthquake
The 1879 Surigao earthquake occurred on June 30 at 18:38 02:55 local time on the northeastern tip of Mindanao. The earthquake with a moment magnitude () of 7.4 struck with an epicenter just south of Lake Mainit. Extensive damage occurred but there were no reports of casualties. Tectonic setting The Philippine Islands is situated in a highly deformed zone between the convergent boundary of the Eurasian and Philippine Sea plates, known as the Philippine Mobile Belt. Along the east, the Philippine Sea Plate subducts beneath the islands at the Philippine and East Luzon trenches. Major subduction complexes are also active along the southwestern coast of Mindanao at the Cotabato Trench and along the Manila Trench of the west Luzon. Running through the Philippine Mobile Belt is the Philippine Fault System; a 1,200-kilometer-long, highly segmented strike-slip fault system. This left-lateral system of faults runs from southeastern Mindanao to northwestern Luzon. Strike-slip deformati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Philippine Standard Time
Philippine Standard Time (PST or PhST; fil, Pamantayang Oras ng Pilipinas), also known as Philippine Time (PHT), is the official name for the time zone used in the Philippines. The country only uses one time zone, at an offset of UTC+08:00, but has used daylight saving time for brief periods in the 20th century. Geographic details Geographically, the Philippines lies and 126°34′ east of the Prime Meridian, and is physically located within the UTC+08:00 time zone. Philippine Standard Time is maintained by the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA). The Philippines shares the same time zone with China, Taiwan, Hong Kong, Macau, Malaysia, Singapore, Western Australia, Brunei, Irkutsk, Central Indonesia, and most of Mongolia. History Philippine Standard Time was instituted through Batas Pambansa Blg. 8 (that defined the metric system), approved on December 2, 1978, and implemented on January 1, 1983. The Philippines is one o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Philippine Fault System
The Philippine Fault System is a major inter-related system of geological faults throughout the whole of the Philippine Archipelago, primarily caused by tectonic forces compressing the Philippines into what geophysicists call the Philippine Mobile Belt. Some notable Philippine faults include the Guinayangan, Masbate and Leyte faults. Philippine Mobile Belt The Philippine Mobile Belt is composed of a large number of accretionary blocks and terranes. These terranes are long and narrow like the Zambales ophiolites which is at least 400 km long and 50 km wide. The strips generally run north–south and the zones of convergence are usually demarcated by fault lines. The Philippine Mobile Belt is compressed on the west by the Eurasian Plate and two arms of the Sunda Plate, and on the east by the Philippine Sea Plate. These tectonic plates have compressed and lifted parts of the Philippines causing extensive faulting, primarily on a north–south axis. All faults in the P ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Butuan
Butuan (pronounced ), officially the City of Butuan ( ceb, Dakbayan sa Butuan; Butuanon: ''Dakbayan hong Butuan''; fil, Lungsod ng Butuan), is a 1st class highly urbanized city in the region of Caraga, Philippines. It is the ''de facto'' capital of the province of Agusan del Norte where it is geographically situated but has an administratively independent government. According to the 2020 census, it has a population of 372,910 people. It served as the former capital of the Rajahnate of Butuan before 1001 until about 1521. The city used to be known during that time as the best in gold and boat manufacturing in the entire Philippine archipelago, having traded with as far as Champa, Ming, Srivijaya, Majapahit, and the Bengali coasts. It is located at the northeastern part of the Agusan Valley, Mindanao, sprawling across the Agusan River. It is bounded to the north, west and south by Agusan del Norte, to the east by Agusan del Sur and to the northwest by Butuan Bay. Butuan w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paleoseismology
Paleoseismology looks at geologic sediments and rocks, for signs of ancient earthquakes. It is used to supplement seismic monitoring, for the calculation of seismic hazard. Paleoseismology is usually restricted to geologic regimes that have undergone continuous sediment creation for the last few thousand years, such as swamps, lakes, river beds and shorelines. In this typical example, a trench is dug in an active sedimentation regime. Evidence of thrust faulting can be seen in the walls of the trench. It becomes a matter of deducting the relative age of each fault, by cross-cutting patterns. The faults can be dated in absolute terms, if there is dateable carbon, or human artifacts. Many notable discoveries have been made using the techniques of paleoseismology. For example, there is a common misconception that having many smaller earthquakes can somehow 'relieve' a major fault such as the San Andreas Fault, and reduce the chance of a major earthquake. It is now known ( ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Surface Rupture
In seismology, surface rupture (or ground rupture, or ground displacement) is the visible offset of the ground surface when an earthquake rupture along a fault affects the Earth's surface. Surface rupture is opposed by buried rupture, where there is no displacement at ground level. This is a major risk to any structure that is built across a fault zone that may be active, in addition to any risk from ground shaking. Surface rupture entails vertical or horizontal movement, on either side of a ruptured fault. Surface rupture can affect large areas of land. __TOC__ Lack of surface rupture Not every earthquake results in surface rupture, particularly for smaller and deeper earthquakes. In some cases, however, the lack of surface effects is because the fault that moved does not reach the surface. For example, the 1994 Northridge earthquake had a moment magnitude of 6.7, caused major damage in the Los Angeles area, occurred at below the Earth's surface, but did not cause surface ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
San Francisco, Surigao Del Norte
San Francisco, officially the Municipality of San Francisco ( Surigaonon: Lungsod nan San Francisco; tl, Bayan ng San Francisco), is a 5th class municipality in the province of Surigao del Norte, Philippines. According to the 2020 census, it has a population of 15,347 people. History There has been many stories concerning the origin of the town but the most common is about the two lovers, Anao and Aon. Anao was a handsome, strong hunter who fell in love with Aon, the most beautiful woman and daughter of a powerful datu, who ruled the town, which was formerly a barangay. Anao and Aon vowed to be true to their love, despite the datu's objection. The datu wanted to break their love, however, he failed since the lovers were found dead near the riverbank in cold embrace. Thus, the name Anao-aon in memory of the two lovers. Anao-aon became a pueblo after the abolition of the encomienda system in the early part of the Spanish regime with Lorenzo Tremedal, a bonafide resident of Surigao, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fault Scarp
A fault scarp is a small step or offset on the ground surface where one side of a fault has moved vertically with respect to the other. It is the topographic expression of faulting attributed to the displacement of the land surface by movement along faults. They are exhibited either by differential movement and subsequent erosion along an old ''inactive'' geologic fault (a sort of old rupture), or by a movement on a recent active fault. Characteristics Fault scarps often contain highly fractured rock of both hard and weak consistency. In many cases, bluffs form from the upthrown block and can be very steep. The height of the scarp formation is equal to the vertical displacement along the fault. Active scarps are usually formed by tectonic displacement, e.g. when an earthquake changes the elevation of the ground and can be caused by any type of fault, including strike-slip faults, whose motion is primarily horizontal. This movement is usually episodic, with the height of the blu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Modified Mercalli Intensity Scale
The Modified Mercalli intensity scale (MM, MMI, or MCS), developed from Giuseppe Mercalli's Mercalli intensity scale of 1902, is a seismic intensity scale used for measuring the intensity of shaking produced by an earthquake. It measures the effects of an earthquake at a given location, distinguished from the earthquake's inherent force or strength as measured by seismic magnitude scales (such as the "" magnitude usually reported for an earthquake). While shaking is caused by the seismic energy released by an earthquake, earthquakes differ in how much of their energy is radiated as seismic waves. Deeper earthquakes also have less interaction with the surface, and their energy is spread out across a larger volume. Shaking intensity is localized, generally diminishing with distance from the earthquake's epicenter, but can be amplified in sedimentary basins and certain kinds of unconsolidated soils. Intensity scales empirically categorize the intensity of shaking based on the effec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Meizoseismal Area
The meizoseismal area in an earthquake is the area of maximum damage. For example, in the Charleston, South Carolina, earthquake of 1886, the meizoseismal area was an area about twenty by thirty miles stretching northeast between Charleston and Jedburg and incorporating Summerville. The estimated epicenter was near Middleton Place. References Seismology {{seismology-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1973 Ragay Gulf Earthquake
The 1973 Ragay Gulf earthquake occurred at around 16:30 local time (UTC +8). It was measured as magnitude 7.4 Mw on the moment magnitude scale. It had a maximum intensity of IX (''Violent'') on the MMI, according to the National Geophysics Data Center, while according to the Philippine Institute of Volcanology and Seismology, the tremor had an intensity of VIII (''Very Destructive'') on the PHIVOLCS Earthquake Intensity Scale. It killed 14 people, injured 100 others, and caused an estimated $2 million in damages. Earthquake The epicenter was located around 17 km east northeast of San Andres on the Ragay Gulf with a depth of 33 km (20.5 mi). It was due to the movement of one of the Philippines' largest fault; the Philippine Fault System with the focal mechanism corresponding to strike-slip. Surface rupture and fissures The earthquake produced an onshore surface rupture 30 km along the Guinayangan segment of the Philippine Fault. It also caused left-later ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1990 Luzon Earthquake
The 1990 Luzon earthquake struck the island of Luzon in the Philippines at 4:26 p.m. on July 16 ( PDT) or 3:26 p.m. ( PST) with an estimated moment magnitude of 7.7 and a maximum Mercalli intensity of IX (''Violent'') and produced a 125 km-long ground rupture that stretched from Dingalan, Aurora to Kayapa, Nueva Vizcaya. The event was a result of strike-slip movements along the Philippine Fault and the Digdig Fault within the Philippine Fault System. The earthquake's epicenter was near the town of Rizal, Nueva Ecija, northeast of Cabanatuan City. An estimated 1,621 people were killed, most of the fatalities located in Central Luzon and the Cordillera region. Impact The earthquake caused damage within an area of about 20,000 square kilometers, stretching from the mountains of the Cordillera Administrative Region and through the Central Luzon region. The earthquake was strongly felt in Metropolitan Manila, destroying many buildings and leading to panic a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Earthquake
An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, from those that are so weak that they cannot be felt, to those violent enough to propel objects and people into the air, damage critical infrastructure, and wreak destruction across entire cities. The seismic activity of an area is the frequency, type, and size of earthquakes experienced over a particular time period. The seismicity at a particular location in the Earth is the average rate of seismic energy release per unit volume. The word ''tremor'' is also used for non-earthquake seismic rumbling. At the Earth's surface, earthquakes manifest themselves by shaking and displacing or disrupting the ground. When the epicenter of a large earthquake is located offshore, the seabed may be displaced sufficiently to cause a tsunami. Earthquakes ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
