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A convergent boundary is an area on Earth where two or more lithospheric plates collide. One plate eventually slides beneath the other, a process known as subduction. The subduction zone can be defined by a plane where many earthquakes occur, called the Wadati–Benioff zone. These collisions happen on scales of millions to tens of millions of years and can lead to volcanism, earthquakes, orogenesis, destruction of lithosphere, and deformation. Convergent boundaries occur between oceanic-oceanic lithosphere, oceanic-continental lithosphere, and continental-continental lithosphere. The geologic features related to convergent boundaries vary depending on crust types.
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 zone. They are the principal way by which continental growth is achieved.
The Explorer Plate is an oceanic tectonic plate beneath the Pacific Ocean off the west coast of Vancouver Island, Canada, which is partially subducted under the North American Plate. Along with the Juan de Fuca Plate and Gorda Plate, the Explorer Plate is a remnant of the ancient Farallon Plate, which has been subducted under the North American Plate. The Explorer Plate separated from the Juan de Fuca Plate roughly 4 million years ago. In its smoother, southern half, the average depth of the Explorer plate is roughly 2,400 metres (7,900 ft) and rises up in its northern half to a highly variable basin between 1,400 metres (4,600 ft) and 2,200 metres (7,200 ft) in depth.
A slow earthquake is a discontinuous, earthquake-like event that releases energy over a period of hours to months, rather than the seconds to minutes characteristic of a typical earthquake. First detected using long term strain measurements, most slow earthquakes now appear to be accompanied by fluid flow and related tremor, which can be detected and approximately located using seismometer data filtered appropriately. That is, they are quiet compared to a regular earthquake, but not "silent" as described in the past.
Episodic tremor and slip (ETS) is a seismological phenomenon observed in some subduction zones that is characterized by non-earthquake seismic rumbling, or tremor, and slow slip along the plate interface. Slow slip events are distinguished from earthquakes by their propagation speed and focus. In slow slip events, there is an apparent reversal of crustal motion, although the fault motion remains consistent with the direction of subduction. ETS events themselves are imperceptible to human beings and do not cause damage.
The 2002 Denali earthquake occurred at 22:12:41 UTC November 3 with an epicenter 66 km ESE of Denali National Park, Alaska, United States. This 7.9 Mw earthquake was the largest recorded in the United States in 37 years. The shock was the strongest ever recorded in the interior of Alaska. Due to the remote location, there were no fatalities and only one injury.
Located in the western Pacific Ocean near Indonesia, the Molucca Sea Plate has been classified by scientists as a fully subducted microplate that is part of the Molucca Sea Collision Complex. The Molucca Sea Plate represents the only known example of divergent double subduction (DDS), which describes the subduction on both sides of a single oceanic plate.
The Okinawa Plate, or Okinawa Platelet, is a minor continental tectonic plate in the northern and eastern hemispheres stretching from the northern end of Taiwan to the southern tip of the island of Kyūshū. The Okinawa Plate hosts typical earthquakes, like the 1911 Kikai Island earthquake, and various types of slow earthquakes, including low frequency earthquakes, very low frequency earthquakes, tremor, and slow slip events.
The 1965 Rat Islands earthquake occurred at 05:01 UTC, on 4 February. It had a magnitude of 8.7 and triggered a tsunami of over 10 m on Shemya Island, but caused very little damage.
Susan Y. Schwartz is a scientist at the University of California, Santa Cruz known for her research on earthquakes, through field projects conducted in locations in Costa Rica and the San Andreas Fault.
Subduction polarity reversal is a geologic process in which two converging plates switch roles: The over-lying plate becomes the down-going plate, and vice versa. There are two basic units which make up a subduction zone. This consists of an overriding plate and the subduction plate. Two plates move towards each other due to tectonic forces. The overriding plate will be on the top of the subducting plate. This type of tectonic interaction is found at many plate boundaries.
Emily E. Brodsky is a Professor of Earth Sciences at the University of California, Santa Cruz. She studies the fundamental physical properties of earthquakes, as well as the seismology of volcanoes and landslides.
Laura Martin Wallace is a geodetic principal scientist who works between the University of Texas at Austin and GNS Science in New Zealand. She was elected Fellow of the Royal Society Te Apārangi in 2018.
Marine geophysics is the scientific discipline that employs methods of geophysics to study the world's ocean basins and continental margins, particularly the solid earth beneath the ocean. It shares objectives with marine geology, which uses sedimentological, paleontological, and geochemical methods. Marine geophysical data analyses led to the theories of seafloor spreading and plate tectonics.
Rachel Abercrombie is a seismologist at Boston University known for her research on the process of earthquake ruptures.
Ruth Harris is scientist at the United States Geological Survey known for her research on large earthquakes, especially on how they begin, end, and cause the ground to shake. In 2019, Harris was elected a fellow of the American Geophysical Union who cited her "for outstanding contributions to earthquake rupture dynamics, stress transfer, and triggering".
Oblique subduction is a form of subduction for which the convergence direction differs from 90° to the plate boundary. Most convergent boundaries involve oblique subduction, particularly in the Ring of Fire including the Ryukyu, Aleutian, Central America and Chile subduction zones. In general, the obliquity angle is between 15° to 30°. Subduction zones with high obliquity angles include Sunda trench and Ryukyu arc.
Simon L. Klemperer is a geophysicist and professor of Geophysics and Geological Sciences at Stanford University. He is best known for his contribution in lithospheric structure and tectonics studies.
The earthquake cycle refers to the phenomenon that earthquakes repeatedly occur on the same fault as the result of continual stress accumulation and periodic stress release. Earthquake cycles can occur on a variety of faults including subduction zones and continental faults. Depending on the size of the earthquake, an earthquake cycle can last decades, centuries, or longer. The Parkfield portion of the San Andreas fault is a well-known example where similarly located M6.0 earthquakes have been instrumentally recorded every 30–40 years.
The 1979 Saint Elias earthquake occurred near noon local time on the 28th of February. It measured Mw 7.4–7.6. Though the maximum recorded Modified Mercalli intensity was VII, damages were minimal and there were no casualties due to the remoteness of the faulting. The epicenter lies near the Alaskan border between America and Canada.
References
- ↑ Eberhart-Phillips, Donna (1989). Investigations of crustal structure and active tectonic processes in the Coast Ranges, Central California (Thesis). Stanford, Calif.: [Stanford University, Dept. of Geophysics, School of Earth Sciences]. OCLC 81536587.
- ↑ Fong, Janice (2018-06-20). "Scientists & Academic Federation Members". UC Davis Earth and Planetary Sciences. Retrieved 2021-08-02.
- ↑ Lanza, Federica; Diehl, Tobias; Eberhart-Phillips, Donna; Herwegh, Marco; Fäh, Donat; Wiemer, Stefan (3 March 2021). "3-D Qp and Qs Seismic Attenuation for the Central Alps and their Foreland". Copernicus Meetings. doi:10.5194/egusphere-egu21-8028. S2CID 238054946.
{{cite journal}}: Cite journal requires|journal=(help) - 1 2 "Eberhart-Phillips". Honors Program. Retrieved 30 July 2021.
- ↑ Eberhart-Phillips, Donna; Reyners, Martin (1997). "Continental subduction and three-dimensional crustal structure: The northern South Island, New Zealand". Journal of Geophysical Research: Solid Earth. 102 (B6): 11843–11861. Bibcode:1997JGR...10211843E. doi: 10.1029/96JB03555 . ISSN 2156-2202.
- ↑ Eberhart-Phillips, D. (16 May 2003). "The 2002 Denali Fault Earthquake, Alaska: A Large Magnitude, Slip-Partitioned Event". Science. 300 (5622): 1113–1118. Bibcode:2003Sci...300.1113E. doi:10.1126/science.1082703. PMID 12750512. S2CID 33375651.
- ↑ Hauksson, Egill; Jones, Lucile M.; Hutton, Kate; Eberhart-Phillips, Donna (1993). "The 1992 Landers Earthquake Sequence: Seismological observations". Journal of Geophysical Research: Solid Earth. 98 (B11): 19835–19858. Bibcode:1993JGR....9819835H. doi:10.1029/93JB02384. ISSN 2156-2202.
- ↑ Sieh, K.; Jones, L.; Hauksson, E.; Hudnut, K.; Eberhart-Phillips, D.; Heaton, T.; Hough, S.; Hutton, K.; Kanamori, H.; Lilje, A.; Lindvall, S. (1993-04-09). "Near-Field Investigations of the Landers Earthquake Sequence, April to July 1992". Science. 260 (5105): 171–176. Bibcode:1993Sci...260..171S. doi:10.1126/science.260.5105.171. ISSN 0036-8075. PMID 17807175. S2CID 35294373.
- ↑ Perlman, David (2009-05-13). "Researchers study earthquakes' effect on delta". SFGATE. Retrieved 2021-08-02.
