eltanin fracture zone

Sykes & Menke (2006) calculated maximum-likelihood estimates of COV that were 0.3 or smaller for a number of large-to-great earthquakes that ruptured nearly the same segments of strike-slip and subduction zone faults. This experiment addresses one component of the potential bias that may be present in CMT seismic moments. R.E. [2] However, the total offset is about 1600km. Hirth The data for Mw > 5.9 are fit remarkably well by the slip predictable model of Shimazaki & Nakata (1980) whereby the size of the next earthquake is proportional to the time since the previous event. Correct Option: O They are the scars on the seafloor basalt that are created by offsets in the mid-ocean ridge. It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide, This PDF is available to Subscribers Only. The Eltanin Fault System(Eltanin Fracture Zone) is a series of six or seven dextral transform faults that offset the Pacific-Antarctic Ridge, a spreading zone between the Pacific Plateand the Antarctic Plate. J. Most prominent is an asymmetric transverse ridge, at which abyssal hills adjacent to the fault zone have been . This includes the HGLP, SRO and ASRO networks in the 1970s, the SRO, ASRO, DWWSSN, CDSN and Geoscope networks for the 1980s, and the IRIS/USGS GSN, Geoscope, GEOFON and MedNet networks since the 1990s. Stewart For the larger and more complex 2001 earthquake the rupture initiation depth is 8.9 km, and the centroid depth, taking into account the propagation of the point source in the direction of the directivity vector, is approximately 11 km, about 7 km below the ocean floor. How that may vary along strike and affect seismic coupling is unknown. The fault segment between -665 and -680 km (green symbols in Fig. A.M. FRACTURE ZONE. Shen The seismic history of the Eltanin Fracture Zone on the Pacific-Antarctic Ridge for the years 1920-81 shows that the seismic slip accumulated during this recording interval accounts for only a small fraction (<10%) of the amount of slip predicted by kinematic models of plate motion. The western part of the transverse ridge consists of fragments of uplifted oceanic crust and upper mantle. Major differences in seismic coupling along strike are not in accord with common thermal models of plate cooling but instead are attributed to varying degrees of metamorphism, rock type and effective normal stress and possibly to the presence of short intratransform spreading centres. According to the normal scenario for the opening of the South Atlantic, it is spreading at a rate of 1.75 cm/year (0.69 in/year) and began forming about 50 Ma. For the period 19902009, we rejected only one event, which occurred on 2001 August 6. Specifically, in the study of the Eltanin earthquakes, we have obtained depths ranging from the shallowest used in the CMT algorithm (12 km) to 26 km. right. Stewart & Okal (1983) modelled P and reflected body waves for several strike-slip events along the Eltanin system. The synthetic waveforms used in the CMT inversion are corrected for lateral heterogeneity using the whole-mantle model of Dziewonski & Woodward (1992) for the body waves and long-period mantle waves, and the phase-velocity maps of Ekstrm et al. 7 for events of Mw > 5.55 (blue) and Mw > 5.9 (red). Four of them have T-axes nearly perpendicular to those transforms while the smallest of Mw 5.3 in 1982 is oriented about 45 to the Tharp. Bergman S.M. The segment of the Heezen transform between 29 and 71 km (Fig. However, a major offset developed on this transform between 60 and 80 Ma, prior to the oldest dated rocks from the ridge. Sykes Hence, a variety of rupture behaviours, repeat times and maximum observed magnitudes is associated with the active parts of the three transforms. 4. . We also analysed the P waves of the two largest normal-faulting events, those of 2001 and 2007 (Fig. They also report reverse faulting events near transform faults at other plate boundaries, another indication of changes in relative plate motion during the last few million years. An up-to-date map of the Antarctic Circumpolar Current (ACC) fronts is constructed from the latest version of mean dynamic topography from satellite altimetry (Park et al., 2019, Observations of the Antarctic Circumpolar Current over the Udintsev Fracture Zone, the narrowest choke point in the . As it flows north, it is constrained by numerous obstacles on the seafloor. What causes the formation of offsets in the mid-ocean ridge system? The seismic history of the Eltanin Fracture Zone on the Pacific-Antarctic Ridge for the years 1920-1981 shows that the seismic slip accumulated during this recording interval accounts for only a small fraction (less than 10%) of the amount of slip predicted by kinematic models of plate motion. Added to Thesaurus in 1989. Pacific Ocean Topography 70%. F. Dziak The Atlantis Fracture Zone (30 N) is one of the smallest transform faults along the Mid-Atlantic Ridge with a spatial offset of 70 km and an age offset of ~ 6 Ma. Bathymetric Features 67%. Distances in kilometres same as in Fig. S. Carbotte (written communication, 2011 July 22) notes that the concentration of earthquakes at the eastern end of the Heezen transform corresponds with the region where the inside Corner Rift' of Lonsdale (1994) is found to the north. In this method, the moment tensor and source centroid are estimated by matching observed long-period three-component seismograms to synthetic waveforms calculated using normal-mode summation. Wolfe et al. Centroid moment tensor solutions are recomputed for 190 earthquakes from 1976 to 2010 along the Heezen, Tharp and Hollister transform faults of the Eltanin system using a 3-D seismic velocity model. Those estimates are smaller than those for oceanic transforms at much slower moving plate boundaries, which is in accord with the notion, which we accept, that temperatures are higher at a given depth for fast moving plate boundaries. We obtained a CMT solution for an additional earthquake of Mw 6.15 in 1979. "fault" or "fault line". 2006). Three normal-faulting events were found with T-axes nearly perpendicular to the Heezen transform (Fig. Duncan T.H. For the Eltanin events, this bias is unlikely to be larger than 15 per cent, even for the events with the deepest calculated centroids. Tromp Moment release over 35 yr per unit length along strike for each of those segments is 3.5 0.7 1014 N m m-1. M.S. . fault zone where the two blocks/plates on either side move side by Chou Their average repeat time is 7.1 yr and their COV is 0.28. Tolstoy trench to the Eltanin Fracture Zone. [5], The hydrothermal vents of the MAR support many life forms. Two 20-km segments of the Hollister transform (Figs 3 and 6) are the sites of several earthquakes of Mw= 5.9 whereas only single shocks of that size are found along its western half. C.J. 2006-01-01. Smith They are the scars on the seafloor basalt that are created by offsets in the mid-ocean ridge. Our findings are in contrast to the widely stated notion that oceanic transform faults, especially those at fast spreading plate boundaries, are poorly coupled with perhaps the presence of occasional stuck patches or asperities. Individual ridge segments trend, how- ever, up to a few tens of degrees from the smooth trend. Lamont-Doherty Earth Observatory Contribution 7505. transform fault, in geology and oceanography, a type of fault in which two tectonic plates slide past one another. "zone of fracture" in Chinese : , ; ; ,; ; "amsterdam fracture zone" in Chinese : "aseismic fracture zone" in Chinese : 5 and the bathymetric expression of it in Fig. Yellow squares show stations for event of 2007 March 31 of Mw= 6.2; the red hexagons show stations for earthquake of 1983 July 5 of Mw= 6.2. Mammericks (1993) and Abercrombie & Ekstrm (2001) clearly include the uppermost oceanic mantle for earthquakes along three slower moving transform faults in the Equatorial Atlantic. . Bathymetry from Ryan et al. The random variations can be considered a consequence of the complicated trade-offs that occur when noisy data are fit with synthetic seismograms that do not capture the full complexity of wave propagation in the Earth. How are fracture zones like the Eltanin created? We find that one isolated asperity along the Heezen transform ruptures about every 4.0 1.0 yr. We note that our revised catalogue with its additions of more solutions, especially of Mw 5.5-6.0, is more complete than the existing CMT catalogue. They proposed that the Eltanin transforms consisted of small, well-separated asperities that rupture in earthquakes. . 2. T.A. His relocations along the Heezen transform, with one exception, are more tightly clustered than ours. Gee R. . These results suggest that asperities responsible for earthquake release at the Mw > 6 levels vary in size along strike but not much in downdip width. side (rather than on top of or away from one another.) Fig. No thrust-faulting solutions were found. We show events characterized by a predominance of strike-slip faulting that we located since 1976 in red along with the few earthquakes in blue that involved a predominance of normal faulting. Best-fitting linear relationships are drawn through the dates of earthquakes and the seismic moment that had just been accumulated. T. The Eltanin Fault System (Eltanin Fracture Zone) is a series of six or seven dextral transform faults that offset the Pacific-Antarctic Ridge, a spreading zone between the Pacific Plate and the Antarctic Plate.The affected zone of the Pacific-Antarctic Ridge is about 800 km long, between 56 S, 145 W and 54.5 S, 118.5 W, southwest of Easter Island, and about as far as one can get from . 4 and red symbols in Fig. Lonsdale (1994) concludes that a zone of extension north of the Heezen transform developed following a Pliocene change in relative plate motion. Moment magnitudes are given below each solution. [2], The trench has a depth of 7,761m (25,463ft), is 300km (190mi) long and has an average width of 19km (12mi) and allows for a major circulation of deep ocean basin water from the west Atlantic to the east Atlantic basins. G. What did the Nazis begin using gas chambers instead of mobile killing units and shooting squads after a while? Watts Bivalve communities have been reported around vents further south. J.J. L.R. Topographic Map of Eltanin Fracture Zone. Eltanin Fracture Zone on the Elevation Map. His events along what we identify as a well-coupled zone between 29 and 59 km in Fig. Menard They also calculated Mw for three earthquakes in 1969, 1971 and 1973; they and Molnar et al. 8. T. 1). This transform migration was preceded by a process 2517 Ma during which the Miocene shallow-water platform mentioned above reached sea level as the transverse ridge was first uplifted, then deformed, and finally buried under the sea. A 30- to 42-km segment of the Heezen transform fault between 124.05 and 124.75 W was the site of eight shocks of Mw 5.93-6.07 from 1976 to 2010 (Figs 3 and 4) and possibly an earlier event in 1975. (1993) and Lonsdale (1994) concluded that the event of 1984 August 16 (Mw 5.3) was located along a bathymetric trough to the north of the Heezen transform. Lonsdale (1994) states My interpretation is that mechanical coupling across the transform valley allows eastward drag by the old thick Antarctic lithosphere to impede the westward movement away from the rise crest of a 20-30-km-wide adjacent strip of thin, newly accreted Pacific lithosphere'. The surface wave catalogue (Ekstram 2006) starts in 1990, and the magnitude that is associated with events in that catalogue is usually very close to the Mw obtained in a CMT analysis. We refer to the magnitudes derived from those moment tensors as either new or recomputed Mws. CHALLENGER FRACTURE ZONE. (1993) attribute it to one of those small spreading centres. Previously, some epicentral locations in that area were uncertain by as much as 500 km. Which letter is pointing to a transform fault? 4814 km S of Papeete, French Polynesia / pop: 26,357 / local time: 08:09:44.3 2016-08-18, Distances: 3385 km SE of Wellington, New Zealand / pop: 381,900 / local time: 14:34:59.2 2016-05-03 The absence of known earthquakes on the three transforms beyond their bounding ridge crests and the spacing of magnetic anomalies, however, indicate that the Pacific and Antarctic plates are intact today beyond the active parts of those transforms and that the lengths of the transforms are not continuing to grow. 1999). The summit of the transverse ridge is capped by Miocene shallow water limestones that reached above sea level 20 Ma before subsiding abnormally fast. The greater number of stations in the last 20 years permitted CMT solutions to be obtained for a large number of smaller earthquakes, some as small as Mw 5.15. Publisher. Since the length along strike, L, was not determined for individual earthquakes, for the calculations later we took a length of 105 km for the entire eastern end of the Heezen transform, which includes several segments that have ruptured in large shocks (Fig. J.K. The CMT centroid depths for events along the Eltanin system are not accurate enough to define the depths or range of seismic faulting at the level of several to 20 km. Given the uncertainty of its CMT location, we think it is reasonably associated with a previous rupture of the same asperity as in Figs 4 and 7. Unlike all the other countries in the St. Cecilia Archipelago, Eltanin is only comprised of one island. Hence, remote techniques such as seismicity and satellite altimetry provide important constraints on the tectonics, especially for the Tharp and Hollister transforms. We chose one of the Eltanin earthquake of (2009 May 7, Mw= 5.6) for which the CMT centroid depth is 25.7 km, and calculated the CMT at various fixed depths, inverting as usual for all the other parameters. J.J. Bohnenstiehl et al. The new results that include surface wave data are not very different from the earlier results. A transform fault may occur in the portion 4706 km S of Papeete, French Polynesia / pop: 26,400 / local time: 01:42:15.1 2017-06-15 [6] The mechanism in the GCMT catalogue indicates normal faulting, while the reanalysis resulted in a strike-slip mechanism. He found that interevent times for those pairs was tightly clustered around 5 yr with a COV ~ 0.2. M.S. Eltanin Fracture Zone System: IHO-IOC GEBCO Gazetteer of Undersea Feature Names : English: Eltanin Fracture Zone: US BGN Advisory Committee on Undersea Features (ACUF) PlaceType: Fracture Zone : Latitude: 54 8' 16.8" S (-54.137999) Longitude: 127 32' 7.3" W (-127.53537) Min. The CMT locations for the Heezen and Hollister transforms and the eastern end of the Tharp are biased to the south of the bathymetric expression of the transforms (Fig. G. . Where is and what is Eltanin Transform Fault and Fracture Zone? Search for: Recent Posts. Since the depth range (Table 1) of faulting in strike-slip events along the Eltanin is very small, those earthquakes may be occurring just in the crust, only in the uppermost oceanic mantle or a combination of the two. In discriminating the signals of earthquakes from those of underground nuclear explosions low excitation of Rayleigh waves in the narrow period band used for determining Ms may result in a few earthquakes appearing to be explosions. C2 shows that Mw is similar to Ms at larger magnitudes but is 0.40.9 units larger at Mw 5.4. Meteoritic Microfossils in Eltanin Impact Deposits. Molnar Arvidsson Fracture Zones : Mendocino Fracture Zone, Murray Fracture Zone, Molokai Fracture Zone, Clarion Fracture Zone, Clipperton Fracture Zone, Challenger Fracture Zone, Eltanin Fracture Zone, Udintsev Fracture Zone Other Pacific Ocean ocean maps Physiography of the Pacific Ocean Countries and islands of the Pacific Region Antarctic Bottom Water (AABW) flows below the LNADW and reaches down to the seafloor. 8) includes three events that are much larger than the others in that series. The San Andreas Fault zone of western North America. The segment of the Tharp transform between -210 and -241 km has a T of 8 yr, Mw 6.08-6.3 and five events. "eltanin" in Chinese : "fracture zone" in Chinese : ; ; ; ; ; . McGuire (2008) examined 16 pairs of Mw= 5.5 earthquakes that occurred along approximately the same segments of transform faults on the East Pacific Rise to the south and north of the equator. He attributed this to changes in the Euler pole for Pacific-Nasca plate motion during the last several million years. The isobaths are drawn at 500 m intervals between 1900 and 3400 m, from the dataset of Smith and Sandwell (1995). 2). The sense of the rotation is such that one or more offsets between parts of the Tharp transform would be short compressional features rather than spreading centres. We choose to use a greater number of stations as time proceeded rather than use a few common stations as he did. Approximate slopes are denoted by dashed lines. The linearity of the CMT locations along the shorter Hollister transform (Fig. That view was strengthen when Menard reviewed the manuscript and provided an unpublished bathymetric map that included more data in the far southeast Pacific. A.M. Figs 4-6 depict the three Eltanin transforms in greater detail. Some other fault segments with larger events rupture with less certain repeat times of 7-24 yr. Other segments are poorly coupled for shocks of Mw > 5.4 and perhaps smaller. The along strike dimensions and perhaps the downdip widths of asperities must be small for parts of the three Eltanin faults that have not ruptured in events larger than Mw 5.0-5.5. Sedimentary rocks consist of particles derived from the weathering of other from EARTH SCIE 213 at IIT Kanpur The CMT locations for the Tharp transform are rotated several degrees with respect to both the computed transform direction in Fig. Since the 40-km section of the Tharp (Fig. P.M. Cumulative seismic moment release for shocks of Mw > 5.55 from 1976 to 2010 along two segments of Hollister transform fault as indicated in Fig. . R.P. Hence, it and the two larger events occurred along an off-transform feature. J.S. Atwater Formed around Antarctica, the AABW is cold, has low salinity, and high silicate concentration. The North Anatolian Fault is formed along the Anatolian plate The ISC located an event along the segment of Ms= 5.5 on 1975 April 19. . . 8, interaction between the two may well occur. At least one seamount chain, the New England Seamounts, lies in the northwestern Atlantic. Watts et al. m3/(kgs2). Wilson The excitation of the long-period waveforms used in the CMT analysis does not vary rapidly as a function of source depth for shallow-focus earthquakes. The affected zone of the Pacific-Antarctic Ridge is about 800kmlong, between 56 S, 145 W and 54.5 S, 118.5 W,[1] southwest of Easter Island, and about as far as one can get from land on planet Earth (4852.6S 12323.6W). plates. Sunrise: 06:37AM; Sunset: 05:22PM; Day length: 10h 45m; The local time in Stockholm County is currently the same as the solar time. [4] . R.L. To the north of the Eltanin Fracture Zone, a wider compositional diversity seems to occur, including FeTi-basaltsand trachy andesite, than that observed from within and to the south of this fracture zone and on the Chile Rise. We did not use the ISC catalogue for events after 1999. McGuire (2008) also found that 1-d aftershock zones extended 30-50 km along strike for Mw~ 6 main shocks for transforms of the East Pacific Rise near the equator. Series of faults that offset the Pacific-Antarctic Ridge, "Seismicity and Aseismic Slip Along the Eltanin Fracture Zone", "The Pacififi c-Antarctic Ridge between 4115'S and 5245'S: Survey and sampling during the PACANTARCTIC 2 cruise", "Earthquakes along Eltanin transform system, SE Pacific Ocean: fault segments characterized by strong and poor seismic coupling and implications for long-term earthquake prediction", https://en.wikipedia.org/w/index.php?title=Eltanin_Fault_System&oldid=1068451688, Creative Commons Attribution-ShareAlike License 3.0, This page was last edited on 28 January 2022, at 13:46. 3391km (2107mi) WSW of Ushuaia, Argentina Enter the email address you signed up with and we'll email you a reset link. https://earthquake.usgs.gov/earthquakes/eventpage/us20009msm#executive, http://www.emsc-csem.org/Earthquake/earthquake.php?id=504225, http://earthquake.usgs.gov/earthquakes/eventpage/us100049ce#general_summary, Follow Earth Extremities on WordPress.com, MAGNITUDE6.9KERMADEC ISLANDS, NEWZEALAND, MAGNITUDE5.6SOUTHERN MID-ATLANTIC RIDGE, MAGNITUDE5.6EAST OF SOUTH SANDWICHISLANDS, MAGNITUDE6.9KERMADEC ISLANDS, NEW ZEALAND. The normal-faulting event of 2001 August 6 is larger than that of any of the strike-slip events along the three Eltanin transforms. In detailed swath mapping of three ultra fast-moving transforms just to the south of the equator, Searle (1983) found that each consisted of two or more short transforms bounded by very short spreading centres. Montesi Dziewonski

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