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1993 Finisterre Earthquakes
The 1993 Finisterre Range earthquakes occurred in October 1993, beneath the Finisterre Range, north of Markham Valley in Morobe Province, Papua New Guinea. The earthquake sequence began on October 13 with a 6.9 mainshock, followed by 6.5 and 6.7 mainshocks. The complex earthquake sequence seriously damaged many villages in the rural Eastern Papua New Guinea region, generating landslides and killing at least 60 people. Tectonic setting Papua New Guinea is situated in a region where the Pacific, Australian, Caroline and several microplates are converging. At the Huon Peninsula, the Woodlark Plate is moving north, converging beneath the South Bismarck Plate along the Markham Valley. The tectonic motion forms a complex zone of subduction and continental collision zones which affect the region. Due to the location at a major plate boundary zone, Papua New Guinea is struck by earthquakes and tsunamis frequently and is one of the world's most seismically active regions. The Finiste ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thrust Fault
A thrust fault is a break in the Earth's crust, across which older rocks are pushed above younger rocks. Thrust geometry and nomenclature Reverse faults A thrust fault is a type of reverse fault that has a dip of 45 degrees or less. If the angle of the fault plane is lower (often less than 15 degrees from the horizontal) and the displacement of the overlying block is large (often in the kilometer range) the fault is called an ''overthrust'' or ''overthrust fault''. Erosion can remove part of the overlying block, creating a ''fenster'' (or ''window'') – when the underlying block is exposed only in a relatively small area. When erosion removes most of the overlying block, leaving island-like remnants resting on the lower block, the remnants are called ''klippen'' (singular ''klippe''). Blind thrust faults If the fault plane terminates before it reaches the Earth's surface, it is referred to as a ''blind thrust'' fault. Because of the lack of surface evidence, blind thr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Volcanic
A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates are diverging or converging, and most are found underwater. For example, a mid-ocean ridge, such as the Mid-Atlantic Ridge, has volcanoes caused by divergent tectonic plates whereas the Pacific Ring of Fire has volcanoes caused by convergent tectonic plates. Volcanoes can also form where there is stretching and thinning of the crust's plates, such as in the East African Rift and the Wells Gray-Clearwater volcanic field and Rio Grande rift in North America. Volcanism away from plate boundaries has been postulated to arise from upwelling diapirs from the core–mantle boundary, deep in the Earth. This results in hotspot volcanism, of which the Hawaiian hotspot is an example. Volcanoes are usually not created where two tectonic plate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ReliefWeb
ReliefWeb is a humanitarian information portal founded in 1996. The portal now hosts more than 720,000 humanitarian situation reports, press releases, evaluations, guidelines, assessments, maps and infographics. The portal is an independent vehicle of information, designed specifically to assist the international humanitarian community in effective delivery of emergency assistance or ''relief''. It provides information as humanitarian crises unfold, while emphasizing the coverage of "forgotten emergencies" at the same time. Origin and development ReliefWeb was founded in October 1996 and is administered by the United Nations Office for the Coordination of Humanitarian Affairs (OCHA). The project began under the US Department of State, Bureau of International Organization Affairs, which had noticed during the Rwanda crisis how poorly critical operational information was shared between NGOs, UN Agencies and Governments. In 1995, the Department's Senior Policy Adviser on Disas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Airstrip
An aerodrome (Commonwealth English) or airdrome (American English) is a location from which aircraft flight operations take place, regardless of whether they involve air cargo, passengers, or neither, and regardless of whether it is for public or private use. Aerodromes include small general aviation airfields, large commercial airports, and military air bases. The term ''airport'' may imply a certain stature (having satisfied certain certification criteria or regulatory requirements) that not all aerodromes may have achieved. That means that all airports are aerodromes, but not all aerodromes are airports. Usage of the term "aerodrome" remains more common in Ireland and Commonwealth nations, and is conversely almost unknown in American English, where the term "airport" is applied almost exclusively. A water aerodrome is an area of open water used regularly by seaplanes, floatplanes or amphibious aircraft for landing and taking off. In formal terminology, as defined by th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Earthquake Rupture
In seismology, an earthquake rupture is the extent of slip that occurs during an earthquake in the Earth's crust. Earthquakes occur for many reasons that include: landslides, movement of magma in a volcano, the formation of a new fault, or, most commonly of all, a slip on an existing fault. Nucleation A tectonic earthquake begins by an initial rupture at a point on the fault surface, a process known as nucleation. The scale of the nucleation zone is uncertain, with some evidence, such as the rupture dimensions of the smallest earthquakes, suggesting that it is smaller than 100 m while other evidence, such as a slow component revealed by low-frequency spectra of some earthquakes, suggest that it is larger. The possibility that the nucleation involves some sort of preparation process is supported by the observation that about 40% of earthquakes are preceded by foreshocks. However, some large earthquakes, such as the M8.6 1950 India - China earthquake., have no foreshocks and it re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Detachment Fault
A detachment fault is a gently dipping normal fault associated with large-scale extensional tectonics. Detachment faults often have very large displacements (tens of km) and juxtapose unmetamorphosed hanging walls against medium to high-grade metamorphic footwalls that are called metamorphic core complexes. They are thought to have formed as either initially low-angle structures or by the rotation of initially high-angle normal faults modified also by the isostatic effects of tectonic denudation. They may also be called denudation faults. Examples of detachment faulting include: *The Snake Range detachment system of the Basin and Range Province of western North America which was active during the Miocene *The Nordfjord-Sogn detachment of western Norway active during the Devonian Period *The Whipple detachment in southeastern California Detachment faults have been found on the sea floor close to divergent plate boundaries characterised by a limited supply of upwelling magma, su ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Décollement
Décollement () is a gliding plane between two rock masses, also known as a basal detachment fault. Décollements are a deformational structure, resulting in independent styles of deformation in the rocks above and below the fault. They are associated with both compressional settings (involving folding and overthrusting) and extensional settings. Origin The term was first used by geologists studying the structure of the Swiss Jura Mountains, coined in 1907 by A. Buxtorf, who released a paper that theorized that the Jura is the frontal part of a décollement at the base of a nappe, rooted in the faraway Swiss Alps. Marcel Alexandre Bertrand published a paper in 1884 that dealt with Alpine nappism. Thin-skinned tectonics was implied in that paper but the actual term was not used until Buxtorf's 1907 publication. Formation Décollements are caused by surface forces, which 'push' at converging plate boundaries, facilitated by body forces (gravity sliding). Mechanically wea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Doublet Earthquake
__NOTOC__ In seismology, doublet earthquakes – and more generally, multiplet earthquakes – were originally identified as multiple earthquakes with nearly identical waveforms originating from the same location. They are now characterized as single earthquakes having two (or more) main shocks of similar magnitude, sometimes occurring within tens of seconds, but sometimes separated by years. The similarity of magnitude – often within 0.4 magnitude – distinguishes multiplet events from aftershocks, which start at about 1.2 magnitude less than the parent shock ( Båth's law) and decrease in magnitude and frequency according to known laws. Doublet/multiplet events also have nearly identical seismic waveforms, as they come from the same rupture zone and stress field, whereas aftershocks, being peripheral to the main rupture, typically reflect more diverse circumstances of origin. Multiplet events overlap in their focal fields (rupture zones), which can be up 100 kilometers across ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Terrane
In geology, a terrane (; in full, a tectonostratigraphic terrane) is a crust fragment formed on a tectonic plate (or broken off from it) and accreted or " sutured" to crust lying on another plate. The crustal block or fragment preserves its own distinctive geologic history, which is different from that of the surrounding areas—hence the term "exotic" terrane. The suture zone between a terrane and the crust it attaches to is usually identifiable as a fault. A sedimentary deposit that buries the contact of the terrane with adjacent rock is called an overlap formation. An igneous intrusion that has intruded and obscured the contact of a terrane with adjacent rock is called a stitching pluton. Older usage of ''terrane'' simply described a series of related rock formations or an area having a preponderance of a particular rock or rock groups. Overview A tectonostratigraphic terrane is not necessarily an independent microplate in origin, since it may not contain the full thickness ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Island Arc
Island arcs are long chains of active volcanoes with intense seismic activity found along convergent tectonic plate boundaries. Most island arcs originate on oceanic crust and have resulted from the descent of the lithosphere into the mantle along the subduction, subduction zone. They are the principal way by which continental growth is achieved. Island arcs can either be active or inactive based on their seismicity and presence of volcanoes. Active arcs are ridges of recent volcanoes with an associated deep seismic zone. They also possess a distinct curved form, a chain of active or recently extinct volcanoes, a Oceanic trench, deep-sea trench, and a large negative Bouguer anomaly on the convex side of the volcanic arc. The small positive gravity anomaly associated with volcanic arcs has been interpreted by many authors as due to the presence of dense volcanic rocks beneath the arc. Inactive arcs are a chain of islands which contains older volcanic and volcaniclastic rocks. Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Suture Zone
In structural geology, a suture is a joining together along a major fault zone, of separate terranes, tectonic units that have different plate tectonic, metamorphic and paleogeographic histories. The suture is often represented on the surface by an orogen or mountain range. Overview In plate tectonics, sutures are the remains of subduction zones, and the terranes that are joined together are interpreted as fragments of different palaeocontinents or tectonic plates. Outcrops of sutures can vary in width from a few hundred meters to a couple of kilometers. They can be networks of mylonitic shear zones or brittle fault zones, but are usually both. Sutures are usually associated with igneous intrusions and tectonic lenses with varying kinds of lithologies from plutonic rocks to ophiolitic fragments. An example from Great Britain is the Iapetus Suture which, though now concealed beneath younger rocks, has been determined by geophysical means to run along a line roughly parallel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thrust Fault
A thrust fault is a break in the Earth's crust, across which older rocks are pushed above younger rocks. Thrust geometry and nomenclature Reverse faults A thrust fault is a type of reverse fault that has a dip of 45 degrees or less. If the angle of the fault plane is lower (often less than 15 degrees from the horizontal) and the displacement of the overlying block is large (often in the kilometer range) the fault is called an ''overthrust'' or ''overthrust fault''. Erosion can remove part of the overlying block, creating a ''fenster'' (or ''window'') – when the underlying block is exposed only in a relatively small area. When erosion removes most of the overlying block, leaving island-like remnants resting on the lower block, the remnants are called ''klippen'' (singular ''klippe''). Blind thrust faults If the fault plane terminates before it reaches the Earth's surface, it is referred to as a ''blind thrust'' fault. Because of the lack of surface evidence, blind thr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
