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1879 Surigao Earthquake
The 1879 Surigao earthquake occurred on June 30 at 18:38 02:55 Philippine Standard Time, local time on the northeastern tip of Mindanao. The earthquake with a Moment magnitude scale, 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 Trench, Philippine and East Luzon oceanic trench, 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 Fault (geology), strike-slip fault system. This left-la ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Philippine Standard Time
Philippine Standard Time (PST or PhST; ), also known as Philippine Time (PHT), is the official name for the time zone used in the Philippines. The country only uses a single time zone, at an UTC offset, offset of UTC+08:00, but has used daylight saving time for brief periods in the 20th century until July 28, 1990. 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 Oblast, Irkutsk (Russia), Time in Indonesia, Central Indonesia, and time in Mongolia, most of Mongolia. History For 323 years, 9 months, and 4 days, which lasted from Saturday, March 16, 1521 (Julian Calendar), until Monday, December 30, 1844 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Butuan
Butuan (pronounced ), officially the City of Butuan (; Butuanon: ''Dakbayan hong Butuan''; ), is a highly urbanized city and the regional center 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 making it the most populous city in Caraga Region. 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 places 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 Butu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paleoseismology
Paleoseismology is the study of ancient earthquakes using geologic evidence, such as geologic sediments and rocks. It is used to supplement seismic monitoring to calculate 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. Methodology Procedure Paleoseismology studies start with finding an active fault. The definition of an active fault can vary, but it is usually based on having tectonically deformed quaternary-age materials that can potentially cause earthquakes. Satellite imaging with high resolution is often used to find such faults, but because of its resolution limitations, there are also other methods such as ground-penetrating radar (GPR), aeromagnetic surveys, and seismic reflection surveys. Faults can be dated in absolute terms using radiocarbon dating. Paleoseismic evidence Evidence of paleoearthquakes ... [...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 (geology), fault affects the Earth's surface. Surface rupture is opposed by buried rupture earthquakes, 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 fault, 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. 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 scale, moment magnitude of 6.7, caused major damage in the Los Angeles a ... [...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; ), is a 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, as the Kapitan del Pueblo. During ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fault Scarp
A fault scarp is a small step-like offset of the ground surface in which one side of a fault has shifted vertically in relation to the other. The topographic expression of fault scarps results from the differential erosion of rocks of contrasting resistance and the displacement of land surface by movement along the fault. Differential movement and erosion may occur either along older inactive geologic faults, or recent active faults. Characteristics Fault scarps often involve zones of highly fractured rock and discontinuities of hard and weak consistencies of rock. Bluffs can form from upthrown blocks and can be very steep, as in the case of Pakistan's coastal cliffs. The height of the scarp formation tends to be defined in terms of the vertical displacement along the fault. Active scarp faults may reflect rapid tectonic displacement and can be caused by any type of fault including strike-slip faults. Vertical displacement of ten meters may occur in fault scarps in volcanic bed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Modified Mercalli Intensity Scale
The Modified Mercalli intensity scale (MM, MMI, or MCS) measures the effects of an earthquake at a given location. This is in contrast with the seismic magnitude usually reported for an earthquake. Magnitude scales measure the inherent force or strength of an earthquake — an event occurring at greater or lesser depth. (The "" scale is widely used.) The MMI scale measures intensity of shaking, at any particular location, on the surface. It was developed from Giuseppe Mercalli's Mercalli intensity scale of 1902. While shaking experienced at the surface is caused by the seismic energy released by an earthquake, earthquakes differ in how much of their energy is radiated as seismic waves. They also differ in the depth at which they occur; deeper earthquakes have less interaction with the surface, their energy is spread throughout a larger volume, and the energy reaching the surface is spread across a larger area. Shaking intensity is localised. It generally diminishes with dist ... [...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 measured 7.4 and had a maximum intensity of IX (''Violent'') on the Modified Mercalli intensity scale. The Philippine Institute of Volcanology and Seismology assigned a maximum 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 damage. Earthquake The epicenter was located around 17 km east northeast of San Andres in 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-lateral offset on a beach line for approximately 3.2 meters. There were also fissures, one of them ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1990 Luzon Earthquake
The 1990 Luzon earthquake occurred on July 16 at 4:26 p.m. (Daylight saving time in the Philippines, PDT) or 3:26 p.m. (Philippine Standard Time, PST) on the densely populated island of Luzon in the Philippines. The shock had a surface-wave magnitude of 7.8 and produced a 125 km-long surface rupture, ground rupture that stretched from Dingalan to Kayapa. The event was a result of strike-slip movements along the Philippine Fault and the Carranglan, Nueva Ecija#Barangays, Digdig Fault within the Philippine fault system. The earthquake's epicenter was near the town of Rizal, Nueva Ecija, northeast of Cabanatuan. An estimated 1,621 people were killed, most of the fatalities located in Central Luzon and the Cordillera Administrative Region, Cordillera region. Geology The Philippine archipelago represents a complex plate boundary between the Philippine Sea and Eurasian plates. To the east, oceanic lithosphere subducts westwards beneath the islands along the Philippine T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Earthquake
An earthquakealso called a quake, tremor, or tembloris the shaking of the Earth's surface resulting from a sudden release of energy in the lithosphere that creates seismic waves. Earthquakes can range in intensity, from those so weak 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. The seismicity at a particular location in the Earth is the average rate of seismic energy release per unit volume. In its most general sense, the word ''earthquake'' is used to describe any seismic event that generates seismic waves. Earthquakes can occur naturally or be induced by human activities, such as mining, fracking, and nuclear weapons testing. The initial point of rupture is called the hypocenter or focus, while the ground level directly above it is the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
