eltanin fracture zone

Watts et al. "eltanin" in Chinese : "fracture zone" in Chinese : ; ; ; ; ; . Woodhouse Boettcher The four estimates of W in Table 1 range from 3.9 to 6.0 km. Examine the figure above. Other short spreading centres may exist along the Tharp and other parts of the Heezen transforms. We find that seismic coupling is not merely a function of relative plate velocity, location along the transform and transform length. Bivalve communities have been reported around vents further south. Their surface wave magnitudes, Ms, are plotted. Events of Mw > 5.9 account for 70 per cent of the moment in Fig. They were generally too small to generate stable CMT results. Their length, relative simplicity, 80 mm yr-1, long-term slip rate and the lack of known shocks of Mw > 7 make them a good laboratory for studying quasi-periodic recurrence of earthquakes on a timescale of years to a few decades. Thermal models with constant and variable mineral physics properties are formally analyzed for fits against recently filtered databases for heat flow and topography. They represent a good laboratory for examining fault segments that slip aseismically, others that are well coupled, and the short recurrence times of earthquakes. M.D. 1975; Lonsdale 1994), which were named for M. Tharp, B. Heezen and C. Hollister (Fig. They concluded from analyses of seismograms, however, that the transform earthquakes themselves did not have a significant component of slow seismic slip. The remarkable quasi-repeatability of events of Mw > 5.9 may be attributed to the isolation of an asperity, that is, a single resisting fault segment that ruptures mainly or solely in earthquakes. Weissel It bisects the Mid-Atlantic Ridge (MAR) just north of the equator at the narrowest part of the Atlantic between Brazil and West Africa, extending from 2N to 2S and from 16W to 20W. . . I.A. Maternovskaya If the anomalous trend is real, having one group of events (east or west) off the primary transform then almost becomes a necessary interpretation. North of and parallel to the fracture zone is a transverse ridge which is particularly prominent over hundreds of kilometres east and west of the MAB of the South Atlantic. The transform valley is 15-20 km wide and 2-4 km deep. plates. 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. [1] The two major faults in the Eltanin Fracture Zone are the Heezen Fault and the Tharp Fault. We report the unique occurren et al. The 'Ar-39Ar dating of rocks dredged either side of the break suggest that it is analogous to the bend in the Hawaiian-Emperor seamount chain. Use the facts stated above when they apply. Depths modelled by Wolfe et al. . [3], Series of faults that offset the Pacific-Antarctic Ridge. Instead, we have chosen not to use models of the depth of seismic faulting in estimating coupling but to calculate downdip width from a segments length along strike, moment release rate and relative plate rate assuming' full seismic coupling. In studies of transforms along the ultra-fast spreading East Pacific Rise just to the south of the equator, McGuire et al. The time intervals again are well fit by the slip predictable model (dotted red line). Larson Menke DeMets Eltanin Fracture Zone. Incidences of 20,538 trochanteric and femoral neck fractures in adult Swedish men and women, from a computerized medical information register for all hosp 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. Montesi These depths are similar to those determined by Wolfe et al. The horizontal axis is parallel to computed transform directions; the vertical is perpendicular to it. The axes are each rotated with respect to the Euler rotation pole of DeMets et al. 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 . Ekstram Bathymetry from Ryan et al. P. Stewart & Okal (1983) modelled P and reflected body waves for several strike-slip events along the Eltanin system. [5], The hydrothermal vents of the MAR support many life forms. Strike-slip CMT solutions from 1976 to 2010 as a function of longitude along the entire Eltanin transform system. The two dotted lines in Fig. Fielding You can help Wikipedia by expanding it. 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. 3391km (2107mi) WSW of Ushuaia, Argentina The existence of three or four plates in the region during those times permitted offset to grow across the Eltanin system (Watts et al. This is a much smaller difference than might have been anticipated from ratios of body-wave radiation amplitudes or other methods. [3], The Romanche Fracture Zone offsets the Mid-Atlantic ridge by 900km (560mi), making it the largest equatorial fracture zone in the Atlantic. 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. T.A. https://session.masteringgeology.com/problemAsset/3004355/4/MGEO_3004355_PartD.jpg. 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 . Strike-slip mechanism in centre is that for 2007 event. The segment of the Heezen transform between 29 and 71 km (Fig. Three normal-faulting events were found with T-axes nearly perpendicular to the Heezen transform (Fig. Is the singer Avant and R Kelly brothers? 11 for Mw > 6. 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. A Seabeam reconnaissance of the 400 km-long fast-slipping (88 mm yr-1) Heezen transform fault zone and the 55 km-long spreading center that links it to Tharp transform defined and bathymetrically described several types of ridges built by tectonic uplift and volcanic construction. 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. Red and green symbols denote strike-slip faulting. Map view of CMT locations of earthquakes along Hollister transform fault from 1976 to 2010. 4). 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. Undersea Features Fishing & Outdoor Fracture Zone Maps: Undersea Features is home to a total of 187 Fracture Zone(s), listed below. [2] However, the total offset is about 1600km. From the scatter of locations perpendicular to the Eltanin transforms, the standard deviation of locations would be around 15 km, after allowing for a constant regional bias. The continuity in smooth trend of the ridge and the Eltanin Fracture Zone suggests some relationship between them. where is and what is eltanin transform fault and fracture. 4, between -25 km and 0 km). At faster separating parts of the Pacific-Antarctic boundary, and on most of the rest of the EPR, fracture zone structure is mainly inherited from the variable arrangement of volcanic ridges and tectonic uplifts at the risecrest intersections, rather than from structures formed at the transform valley. No known large earlier events can be readily attributed to the segment between 122 and 141 km in Fig. What kind of fault is represented by the eltanin and romanche fracture zones? 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 . (2007) and others modelled temperatures in the vicinity of oceanic transform faults at fast moving plate boundaries that differ from those for the earlier simple plate cooling models. T. . Where is and what is Eltanin Transform Fault and Fracture Zone. M. The precision of epicentral locations in his study was improved considerably by using data from new seismic stations in Antarctica that were installed during the International Geophysical Year, 1957-1958, and computer programs for analysing P and PKP arrival times. This completeness can be seen as well by the slope of 1.0 of the LogNMw relationship in Fig. Distances in kilometres same as in Fig. The continuity in smooth trend of the ridge and the Eltanin Fracture Zone suggests some relationship between them. We thank S. Carbotte and C. Scholz of Lamont and journal reviewers J. McGuire and C. Laederach for critically examining the manuscript and for valuable suggestions and P.G. Map view of CMT locations of earthquakes along Tharp transform from 1976 to 2010. 4. Approximate slopes are denoted by dashed lines. 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). VanDeMark (2006) analysed the relative locations of earthquakes of moderate magnitude along oceanic transform faults with a double-difference method using Rayleigh waves of periods between 30 and 80 s. He used 92 events along the Eltanin transform faults from 1980 to early 2006, about half of the number we analysed. 7 for events of Mw > 5.55 (blue) and Mw > 5.9 (red). 7; several were the sites of two or three earthquakes of Mw > 6.15. Cumulative seismic moment release 1971 to 2010 along two segments of Tharp transform as indicated in Fig. In the Atlantic Ocean most fracture zones originate from the Mid-Atlantic Ridge, which runs from north to south, and are therefore west to east oriented in general. fault zone where the two blocks/plates on either side move side by 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. We found that Mo evaluated at 10-km depth is 15 per cent smaller than that calculated at the best-fitting centroid depth (25.7 km). Dotted lines denote approximate locations of ridges. The fault segment between -665 and -680 km (green symbols in Fig. D.F. [6] Spreading Centre. Seabeam and SeaMARC II swath-mapping surveys, with ancillary magnetic and gravity profiling, describe the fast-slipping (84-86 mm year1) 380 km-long Heezen transform (56 S) and the 145 km-long Raitt transform (54 S), together with the youngest parts of their rise-flank fracture zones. The few involving normal faulting are located up to 40 km on either side of the transforms and involve extension nearly normal to the transforms. . Sunrise, sunset, day length and solar time for Stockholm County. . For the period 19761989, we selected for analysis all events in the ISC (International Seismological Centre), PDE (Preliminary Determination of Epicentres of the US Geological Survey) and GCMT catalogues, regardless of magnitude. They proposed that the Eltanin transforms consisted of small, well-separated asperities that rupture in earthquakes. R.C. -Linear spreading on Earth's curved surface. -Different segments of the mid-ocean ridge system spreading at different rates. By chron 28 (63-64 Ma) about 750 km of the present 1000 km offset had accumulated across them. J. For the four seismically active fault segments in Table 1 we obtain similar downdip widths of seismic faulting of about 5 km assuming coupling at the full plate rate. They differ in that hypocentres derived using body waves give the location of rupture initiation whereas CMT solutions give centroid locations and origin times. 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. The three sets of large events have a repeat time of 13 yr and a COV of 0.13. Their average repeat time is 7.1 yr and their COV is 0.28. Okal & Langenhorst (2000) relocated a number of earthquakes along the three transforms using short-period body waves. His relocations along the Heezen transform, with one exception, are more tightly clustered than ours. L.R. J.J. There are about 300 fracture zones, with an average north-south separation of 55 kilometres (34 mi): two for each degree of latitude. J. We also analysed the P waves of the two largest normal-faulting events, those of 2001 and 2007 (Fig. D.W. Blue symbols indicate four normal faulting mechanisms and their T-(extensional) axes. (1981), Arvidsson & Ekstrm (1998) and Ekstrm et al. Lamont-Doherty Earth Observatory Contribution 7505. Jordan Fig. Solutions for new earthquakes of Mw > 5.5 were not found after early 2002. Haiti is situated on a transform boundary also known as a strike Others related faults include the Vacquier Transform Fault, the Menard Transform Fault, and the Udintsev Fault. That Ms was obtained using a single station. Only the Heezen transform has been surveyed by swath mapping (Lonsdale 1994). Behn It is therefore unlikely that the event selection for 19902009 missed any earthquake with a moment magnitude greater than 5.5. Dotted lines denote approximate locations of ridge segments. The completeness of the CMT data set as a function of time is described later. Search for other works by this author on: Earthquake slip on oceanic transform faults, Global CMT analysis of moderate earthquakes, Mw 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 . Log of cumulative number of earthquakes per 20 yr larger than a given Mw as a function of Mw. 2006-01-01. 8) includes three events that are much larger than the others in that series. The relationship between the two events that occurred on the same day with computed CMTs only 5 km apart is unknown. Small amounts of normal faulting occurring off transform is in accord with the idea that the Euler pole has moved relatively recently in time to place each of the three transform zones under a small component of extension. Pacific Ocean depth map showing the Heezen Fault and the Tharp Fault as #17. Symbols, axes and origin of coordinates same as Fig. E.J. Boettcher 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. Fracture zone evolution is investigated using dynamic models that allow the fault zones to freely slip. We present a compilation of the seismic properties of the Eltanin Transform Fault (TF) system, compelled by the recent discovery of the Hollister Ridge and the possibility of a change of plate. Whether the depths obtained for normal-faulting events, which occurred off the transforms, applies to strike-slip events along the transforms themselves is equivocal since the velocity and thermal structure of the three transforms is not known and close-in observations with ocean bottom instruments have not been made. The CMT methodology and format of the catalogue are described in Dziewonski (1981) and Ekstram (2005). The morphology of the Atlantis Fracture Zone is typical of that of slow-slipping transforms. 5 contains only two earthquakes of Mw 5.45 and 5.50. This is not surprising since all stations are at large teleseismic distances. With that assumption we obtain downdip widths of about 5 km for four segments of the Heezen, Tharp and Hollister transforms. FRACTURE ZONE. 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. One 30-42-km-long segment of the Heezen transform that appears to be an isolated well-coupled asperity has ruptured in eight earthquakes of Mw 5.9-6.1 quasi-periodically with a coefficient of variation of 0.26 every 4.0 1.0 yr. Other well-coupled fault segments, which were sites with earthquakes up to Mw 6.39 and fewer events since 1976, have average repeat times of about 7-24 yr. Wilson Topographic Map of Eltanin Fracture Zone. G. Clearly, a gradient in the maximum size of earthquakes and seismic coupling occurs between the eastern and western ends of the Heezen transform. Thus, the use of the CMT methodology insured more complete coverage of earthquakes in this very remote area of the Earth. As in Fig. The two largest (Mw 6.7 and 5.9) occurred well to the north of the transform in 2001 and 2007. The summit of the transverse ridge is capped by Miocene shallow water limestones that reached above sea level 20 Ma before subsiding abnormally fast. Farther west activity decreases to a maximum of Mw 5.9-6.1 between +30 and +100 km along the fault and then again to a maximum of Mw 5.6-5.8 between +10 and 30 km. Moment release in earthquakes of Mw= 6.08 is about 60 per cent of that for Mw > 5.55. The presence of large events just to its west and the variety of Mws, however, suggest that it does not always rupture as a single asperity. 1975; Lonsdale 1994), which were named for M. Tharp, B. Heezen and C. Hollister . 11 between Mw 5.4 and 6.0 for events from 1991 to 2010. These segments contain fewer events of Mw > 5.9 than that in Fig. 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. G. Indeed, jets are observed to pass along both the Udinstev and Eltanin Fracture Zones (Gille 1994; Hughes and Ash 2001).

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