Publisher. Our calculations of moment magnitude Mw are compared with determinations of the short-period magnitude mb in Fig. 5) and the 42-km section of the Heezen (Figs 4 and 7) are well isolated from other large shocks along those transforms we took the scatter in locations along them as a measure of L. Our knowledge of L is limited otherwise by the paucity of aftershocks of Mw > 5-5.5. 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. . He attributed this to changes in the Euler pole for Pacific-Nasca plate motion during the last several million years. 4786 km SE of Avarua, Cook Islands / pop: 13,400 / local time: 01:42:15.1 2017-06-15, http://www.emsc-csem.org/Earthquake/earthquake.php?id=524555, Distances: 4676 km SE of Wellington, New Zealand / pop: 381,900 / local time: 06:09:44.3 2016-08-19 J. D.K. J.H. What causes the formation of offsets in the mid-ocean ridge system? [8], Coordinates: .mw-parser-output .geo-default,.mw-parser-output .geo-dms,.mw-parser-output .geo-dec{display:inline}.mw-parser-output .geo-nondefault,.mw-parser-output .geo-multi-punct{display:none}.mw-parser-output .longitude,.mw-parser-output .latitude{white-space:nowrap}000N 1800W / 0.000N 18.000W / 0.000; -18.000, "Dolomite formation in pelagic limestone and diatomite, Romanche Fracture Zone, Equatorial Atlantic", 10.1175/1520-0485(1998)028<1929:MITRFZ>2.0.CO;2, "Lower Cretaceous to Eocene sedimentary transverse ridge at the Romanche Fracture Zone and the opening of the equatorial Atlantic", "Hydrothermal activity on the southern Mid-Atlantic Ridge: Tectonically- and volcanically-controlled venting at 45S", "Transport of Bottom Water in the Romanche Fracture Zone and the Chain Fracture Zone", 10.1175/1520-0485(1998)028<0779:TOBWIT>2.0.CO;2, "Biodiversity and biogeography of hydrothermal vent species: thirty years of discovery and investigations", https://en.wikipedia.org/w/index.php?title=Romanche_Trench&oldid=1090955796, This page was last edited on 1 June 2022, at 10:32. 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. Also, there was no discontinuous change in the calculated Mo when the CMT was evaluated above the Moho (which in PREM is at 24.4 km) or below it. It is therefore unlikely that the event selection for 19902009 missed any earthquake with a moment magnitude greater than 5.5. C2 shows that Mw is similar to Ms at larger magnitudes but is 0.40.9 units larger at Mw 5.4. To address part of this question, we performed the following experiment. Marathon Expedition, Leg 6 Studies in the Tonga Trench, Louisville Ridge, and Eltanin Fracture Zone . Thus, the use of the CMT methodology insured more complete coverage of earthquakes in this very remote area of the Earth. 7. Search for: Recent Posts. J. Ekstram The CMT methodology and format of the catalogue are described in Dziewonski (1981) and Ekstram (2005). Lynn R. Sykes, Gran Ekstrm, Earthquakes along Eltanin transform system, SE Pacific Ocean: fault segments characterized by strong and poor seismic coupling and implications for long-term earthquake prediction, Geophysical Journal International, Volume 188, Issue 2, February 2012, Pages 421434, https://doi.org/10.1111/j.1365-246X.2011.05284.x. Stewart & Okal (1983) modelled P and reflected body waves for several strike-slip events along the Eltanin system. Dziewonski . G. The feature was then named the Eltanin fracture zone. A.B. florida a jurassic transform plate boundary. H.W. 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. That segment may well not be a single isolated an asperity as that in Fig. 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 . FRACTURE ZONE. 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. No thrust-faulting solutions were found. Indeed, jets are observed to pass along both the Udinstev and Eltanin Fracture Zones (Gille 1994; Hughes and Ash 2001). Louisville chain has been related to the Eltanin fracture zone in several models (Hayes and Ewing, 1971;Larson and Chase, 1972;Watts et al., 1988). Challenger Fracture Zone. 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. 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. A.M. Since the 40-km section of the Tharp (Fig. The fast rate of plate motion, maximum size of events and relatively short repeat times make these fault segments a good laboratory for research on quasi-periodic behaviour and earthquake prediction. Nevertheless, strike-slip earthquakes along the three transform faults are much more numerous and have together released more seismic moment than the normal-faulting events. Distances in kilometres same as in Fig. NASA Technical Reports Server (NTRS) Kyte, Frank T.; Gersonde, Rainer; Kuhn, Gerhard. We have combined shipboard and Seasat altimeter derived data in an intergrated geological and geophysical study of the Louisville Ridge; a 3500kmlong seamount chain extending from the Tonga trench to the Eltanin Fracture Zone. This is not surprising since all stations are at large teleseismic distances. Note exaggerated scale in transform-perpendicular direction. Where is and what is Eltanin Transform Fault and Fracture Zone. . S1 in the Supporting Information shows the revised CMT solutions for 186 earthquakes from 1976 to 2009 on the left and those in the online catalogue on the right. . The Antarctic-Pacific Plate boundary, while characterized by somewhat slower rates than segments of the East Pacific Rise farther north, contains three nearby transform faults-the Heezen, Tharp and Hollister-that together are about 1000 km long and have been the sites of numerous earthquakes of moment magnitude, Mw, 5-6.4 during the past 50 years. 2006). Hence, we suspect that the events at the western end of the Tharp transform are anomalous in some sense. [2] However, the total offset is about 1600km. Subsequent locations of earthquakes and mapping of bathymetry and magnetic anomalies showed that the Eltanin zone consisted of three en echelon transforms (Molnar et al. Blue symbols indicate four normal faulting mechanisms and their T-(extensional) axes. Seismicity and aseismic slip along the Eltanin Fracture Zone ( Pacific The RSS includes pelagic material from the early Cretaceous (140 Ma) which, coupled with the thickness of the sequence, does not fit with the normal scenario for the opening of the South Atlantic around the Aptian-Albian (125100 Ma). No thrust earthquake mechanisms, however, were found along the Tharp zone. (1993) attribute it to one of those small spreading centres. Systematic deviations can occur when the Earth structure in the source area deviates significantly from the structure assumed in the calculation of synthetic seismograms, that is, from PREM (Dziewonski & Anderson 1981). www.science.gov 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. T.A. 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. On the basis of serial hydrographic measurements, the Chain Fracture Zone appears to be separated into several deeper sections. . The average repeat time for the eight events of Mw > 5.9 is 4.0 1.0 (1 SD) yr. His results support the idea that events along that segment break a single isolated asperity. The isobaths are drawn at 500 m intervals between 1900 and 3400 m, from the dataset of Smith and Sandwell (1995). As it flows north, it is constrained by numerous obstacles on the seafloor. We find that seismic coupling is not merely a function of relative plate velocity, location along the transform and transform length. 5 contains only two earthquakes of Mw 5.45 and 5.50. 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. Eltanin | St. Cecilia Archipelago Wiki | Fandom 5) are characterized by shocks of Mw= 5.9 but about half of its length is not. The flow of NADW through the Romanche and Chain Fracture Zones may serve as a conduit for larval transport from the western North Atlantic to the eastern South Atlantic. We also used the same 3-D velocity model for our new CMT solutions. . That may account for the variety of Mws along it. We used a box from 54S to 58S and 140W to 120W to identify earthquakes that might be located on the Eltanin transform system. At 14.5W the trough reaches a maximum depth of 2895 fm (5470 m). The zone is in the South Pacific, southwest of Easter Island, between 56 S, 145 W and 54.5 S, 118.5 W. The Dead Sea fault zone is located on a Transform boundary. 7, however, since it is located just to the east of other large shocks along the Heezen transform. Nakata F. Of the 84 earthquakes from 1976 to 1989, we rejected seven CMT solutions. Hence, remote techniques such as seismicity and satellite altimetry provide important constraints on the tectonics, especially for the Tharp and Hollister transforms. and the Eurasian plate. The smaller events in Fig. 2). G. 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. "zone of fracture" in Chinese : , ; ; ,; ; "fracture system" in Chinese : ; "amsterdam fracture zone" in Chinese : Locations of earthquakes with CMT solutions (red) characterized by a predominance of strike-slip faulting along the Heezen, Tharp and Hollister transform faults of the Eltanin system from 1976 to 2010.