The relationship between the two events that occurred on the same day with computed CMTs only 5 km apart is unknown. Fracture Zone. 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. E.A. 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. 4). Swarms of hydrothermal shrimps reminiscent of those found from northern MAR vent-sites have been found on the northern part of the southern MAR. 3). Boettcher Although A.B. The two dotted lines 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 . Ryan and M. Tolstoy for helpful discussions. C.G. Most of the earlier earthquakes analysed here are larger than Mw= 5.5, since smaller earthquakes appear to have gone largely undetected until the 1990s. Most prominent is an asymmetric transverse ridge, at which abyssal hills adjacent to the fault zone have been . Our results indicate considerable variation in moment release and hence in fault coupling along the strike of the three Eltanin transforms. . Correct Option: O They are the scars on the seafloor basalt that are created by offsets in the mid-ocean ridge. 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. R. They are the scars on the seafloor basalt that are created by offsets in the mid-ocean ridge. The centroid epicentre and time did not shift appreciably in these different inversions, nor did the geometry of the moment tensor change appreciably. Our work using much greater numbers of stations and earthquakes confirms the general findings of Stewart and Okal about the abundance of aseismic slip and the presence of asperities. C. Equidistant polar diagram out to distance of 135 centred on our study area, the Eltanin transform system, illustrating distribution of stations that contributed data to CMT solutions. It and some other segments of the three Eltanin transforms appear to be well coupled seismically. -Different segments of the mid-ocean ridge system spreading at different rates. Bohnenstiehl et al. Please see the related question for more information. They conclude that the Blanco and Gofar transforms, which were the target of their study, appear to be comprised of multiple patches on a single fault segment that repeatedly fail in earthquakes that rupture each of those patches. T. Their 1000 km length is greater than that of any other oceanic transforms at fast-spreading plate boundaries. E.J. A.R. Our locations and those of the ISC based on body waves are located systematically about 25 km south of the transforms as mapped in Fig. transform faults fracture zones and the kinematics of. Lonsdale (1994) mapped a small nearby series of short spreading centres along the Heezen transform, one along the Raitt transform farther north and the Udintsev farther south. The repeat times of those largest events are longer but uncertain since they are based on few earthquakes. 4. From 1990 to 2009, we selected events in the ISC, PDE, GCMT and surface wave detection (SWE) catalogues with at least one magnitude equal to or greater than 5.5. 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 kinematics pattern in the region. For the Eltanin events, this bias is unlikely to be larger than 15 per cent, even for the events with the deepest calculated centroids. The maximum size of earthquakes along fast spreading ridges themselves is not greater than magnitude 3 (McGuire 2008; M. Tolstoy, personal communication, 2010). transform plate boundaries learning geology. Wolfe et al. 3292km (2046mi) WSW of Puerto Natales, Chile Eltanin fracture zone fracture zone zone of fracture n. , rock fracture zone Mendocino fracture zone oceanic fracture zone deep fracture zone Charlie Gibbs fracture zone - oceanic floor fracture zone [1] The two major faults in the Eltanin Fracture Zone are the Heezen Fault and the Tharp Fault. The Eltanin Transform Fault and Fracture Zone is a series of six or seven dextral transform faults along ~800 km of the Pacific-Antarctic Ridge that offset it ~1600 km. 6). In the basin on the eastern side of the MAR the Walvis Ridge blocks the northward passage. As AABW flows through the Romanche Fracture Zone, salinity and temperature increase significantly. 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. Where is and what is Eltanin Transform Fault and Fracture Zone? Wolfe et al. (1981), Arvidsson & Ekstrm (1998) and Ekstrm 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 . Smith The morphology of the Atlantis Fracture Zone is typical of that of slow-slipping transforms. Atwater Hence, a variety of rupture behaviours, repeat times and maximum observed magnitudes is associated with the active parts of the three transforms. How are fracture zones like the Eltanin created? They found that between chron 27 (61 Ma) and 34 spreading rates were about twice as high to the north of the two transforms than to their south. plates. (2009). 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. 4). 2. 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. DeMets Fielding Nearby ocean bottom seismometers are needed to detect them. We refer to the magnitudes derived from those moment tensors as either new or recomputed Mws. Thermal models with constant and variable mineral physics properties are formally analyzed for fits against recently filtered databases for heat flow and topography. Four segments of the Tharp transform (Fig. 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. Ekstram They were generally too small to generate stable CMT results. The shaded area is the "Hollister region" whose seismicity is detailed in Fig. Their poorly determined repeat times range from 13 to 24 yr. A transform fault may occur in the portion We find that one isolated asperity along the Heezen transform ruptures about every 4.0 1.0 yr. K. 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). Blue symbols indicate four normal faulting mechanisms and their T-(extensional) axes. D.F. Dziewonski Intermediate-period surface waves have been used in the GCMT analysis since 2004, and often are very useful for constraining solutions for earthquakes smaller than Mw= 5.5. His results support the idea that events along that segment break a single isolated asperity. This is a much smaller difference than might have been anticipated from ratios of body-wave radiation amplitudes or other methods. 4. 4), to constrain their source depths. N.N. Distances in kilometres same as in Fig. Depths modelled by Wolfe et al. 5) are characterized by shocks of Mw= 5.9 but about half of its length is not. Which two plates create the Eltanin Fracture Zone? Lonsdale J. G. 1). Bergman Atwater Distances in kilometres same as in Fig. M. However, a major offset developed on this transform between 60 and 80 Ma, prior to the oldest dated rocks from the ridge. While off-transform normal-faulting events and short intra-transform spreading centres are reasonably attributed to changes in plate motion, we do not find evidence from earthquake mechanisms along the Eltanin transforms that those faults are leaky' today in the sense proposed by Menard & Atwater (1969). We used a box from 54S to 58S and 140W to 120W to identify earthquakes that might be located on the Eltanin transform system. I cover many earth extremities ranging from Earthquakes, Quake Swarms, Volcanic Activity/Eruptions, CME's Coronal Mass Ejections, Solar Flares, Geomagnetic Storms, Magnetosphere Pressure plus other solar related radiation pulses, Asteroid/Meteorite Threats, Solar System Threats, Landslides, Flooding, Sink Holes, Hurricanes, Typhoons, Storms, Tsunami's, prolonged Snowfall/Ice, Heatwaves, Drought, Nuclear Fallout/Leak, Viruses, Deceases, Epidemics, Dead Mammals/Birds/Animals, Pollution Threat Levels and many more events. Their remoteness and rough seas, however, puts a premium on studying them at large distances using seismic waves and various satellite technologies. Kent Previously, some epicentral locations in that area were uncertain by as much as 500 km. 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 Johanson Ships have surveyed the active parts of three Eltanin transforms infrequently since they straddle the pole of inaccessibility' at the farthest point on the Earth from inhabited land (Lonsdale 1994). T.H. and the Eurasian plate. J.J. 7 includes an earthquake on 1981 June 20 of Mw 5.94, which was located just to the east of the others at a time when relatively few stations were available for calculating a CMT location. W. Some of our largest events occur within about 25 km of the eastern end of the Heezen and the western end of the Hollister transforms (Figs 4 and 6). . How are fracture zones like the Eltanin created? 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. west coast of the USA through California. 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. . Wolfe They proposed that the Eltanin transforms consisted of small, well-separated asperities that rupture in earthquakes. Palaeoseismically determined dates for earthquakes along faults of the San Andreas system are uncertain, whereas exact dates are known for the events we examine along the Eltanin transforms. A new analysis of plate cooling models indicates that the properties of oceanic lithosphere may need to be reevaluated, or that additional phenomena beyond the conditions of simple mineral physics plate models are important. 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. 7) has the shortest T, 4.0 yr, Mw 5.93-6.07 and eight events. They are typified by some of the roughest sea conditions and most severe weather on the Earth. . We propose that the remainder of the plate motion . 7 is not unreasonable for single events of Mw 5.9-6.1. This tectonics article is a stub. 11 displays the log of the cumulative number of events per 20 yr as a function of decreasing Mw for the periods 1976-1990 and 1991-2010. Figs 5 and 6 show five other normal-faulting mechanisms adjacent to but not on the Tharp and Hollister transforms. Fig. Weissel 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 Molnar Langenhorst The Eltanin Transform Fault and Fracture Zone is a series of six or seven dextral transform faults along ~800 km of the Pacific-Antarctic Ridge that offset it ~1600 km. 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. Is the singer Avant and R Kelly brothers? They find that aftershock zones of nearby pairs of moderate-size earthquakes along fast-moving transforms were separated by small spreading centres. Which letter(s) is/are pointing to an inactive fracture zone? 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. The ISC located an event along the segment of Ms= 5.5 on 1975 April 19. 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. Fracture zone evolution is investigated using dynamic models that allow the fault zones to freely slip. . 4065 km S of Avarua, Cook Islands / pop: 13,373 / local time: 16:34:59.2 2016-05-02 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. In contrast, VanDeMark (2006) used few events, a double-difference methodology and a uniform velocity model for Rayleigh waves in calculating revised earthquake locations along the Eltanin transforms. R.G. 7. This partitioning of slip likely results from changes during the last few million years in the Euler pole for relative motion between the Antarctic and Pacific plates. If so, their repeat time was about 16 yr but is based on only three events. Larson The normal-faulting event of 2001 August 6 is larger than that of any of the strike-slip events along the three Eltanin transforms. Red and green symbols denote strike-slip faulting. J.H. 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). For example, if it is known that an earthquake occurred at a depth of 10 km, and the CMT was calculated at 25 km, is there a corresponding bias in the CMT estimate of Mo? 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. L.M. Since the number and azimuthal distribution of the global long-period stations used in computing the CMT solutions increased dramatically since 1976, especially in the 1990s, we choose to use digital data from as many stations as possible in our analyses rather than from merely the few that recorded most of the events. The average of the three intervals since 1967 is 12.8 yr with a COV of 0.36. He attributed this to changes in the Euler pole for Pacific-Nasca plate motion during the last several million years. [2] However, the total offset is about 1600km. 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 transform valley is 15-20 km wide and 2-4 km deep. 4 occurred. S.M. They are the scars on the seafloor basalt that are created by offsets in the mid-ocean ridge. We determined a CMT solution for it using seven digital stations and obtained a Mw of 6.1, a strike-slip mechanism and a location (red triangle) about 20 km west of the group indicated in Fig. 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). 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. 7, however, since it is located just to the east of other large shocks along the Heezen transform. Marathon Expedition, Leg 6 Studies in the Tonga Trench, Louisville Ridge, and Eltanin Fracture Zone 1997, 2005). The average displacement per earthquake is 0.32 m assuming full coupling and an average repeat time of 4 yr. Figs 8-10 show cumulative moment release throughout 2010 for seven additional segments of the three Eltanin faults. We also analysed the P waves of the two largest normal-faulting events, those of 2001 and 2007 (Fig. The catalogue for the latter period appears to be complete for Mw > 5.4-5.5 whereas the earlier period is not complete for Mw < 6.0. Dziak 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. For full access to this pdf, sign in to an existing account, or purchase an annual subscription. 2006-01-01. 3) to indicate stationarity of well-coupled and poorly coupled behaviour along transform segments since at least 1969. Searle The eastern part of the transverse ridge, however, consists of a thick sequence of stratified material called the Romanche Sedimentary Sequence (RSS). [] ( ) "eltanin fracture zone" in Chinese : "eltanin" in Chinese : "fracture zone" in Chinese : ; ; ; ; ; . Since the 40-km section of the Tharp (Fig. Hirth which two plates create the eltanin fracture zone quizlet; Well Inspection using ROV at Kondashetti Halli, Bangalore Dziewonski Test the following series for convergence or divergence. Wolfe et al. 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. The boat was returning to France after spending a few months on a scientific mission near Cape Horn as part of the first International Polar Year. If the anomalous trend is real, having one group of events (east or west) off the primary transform then almost becomes a necessary interpretation. Sea-surface shape by satellite Pelagic shrimps of the Family Oplophoridae (Crustacea Decapoda) from the Pacific sector of the Southern Ocean: USNS Eltanin Cruises 10, 11, 14-16, 19-21, 24 . Nearby asperities, as along the eastern part of the Heezen transform, may break either individually or together. Hence, it and the two larger events occurred along an off-transform feature. For the eight fault segments examined in Figs 7-10 some systematic behaviour can be seen among Mws of the largest earthquakes, their average repeat times, T, and the numbers of large events.