eltanin fracture zone

These segments contain fewer events of Mw > 5.9 than that in Fig. H.W. . 4. Lamont-Doherty Earth Observatory Contribution 7505. a) reproduction b) controlling an experiment c) growth and development d) maintaining a steady temperature, An equation for the period T of a planet (the time to make one orbit about the Sun) is, T2=42r3/(GM)T ^ { 2 } = 4 \pi ^ { 2 } r ^ { 3 } / ( G M ) 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. G. These are too small to represent the actual uncertainties. The waveforms were edited using the standard Global CMT (GCMT) automated waveform editor, and inverted using the standard Global CMT computer codes using corrections for 3-D earth structure in the calculation of synthetic seismograms (Ekstram . G. R.E. T. (1988) found that at magnetic chron 34, 83-121 Ma, when New Zealand broke away from Antarctica, there was essentially no fault offset at the location where the Eltanin system was later to develop. J.T. This is in accord with the findings of Stewart & Okal (1983) that the Eltanin system has not broken in great events since 1920 and is unlikely to do so. He concluded that a major fracture zone intersected the mid-oceanic ridge at that location, much like those mapped by Menard (1960) farther north. 11 between Mw 5.4 and 6.0 for events from 1991 to 2010. The transverse ridge separates the present trench from an 800km (500mi)-long aseismic valley where the Romanche transform was located until about 108 Ma. 7 for events of Mw > 5.55 (blue) and Mw > 5.9 (red). C2 shows that Mw is similar to Ms at larger magnitudes but is 0.40.9 units larger at Mw 5.4. Bivalve communities have been reported around vents further south. The Eltanin Transform Fault and Fracture Zone is a series of six or seven dextral transform faults along ~800 km of the. This is an improvement over past formulations where bathymetric offsets were imposed kinematica. We choose to use a greater number of stations as time proceeded rather than use a few common stations as he did. Smith 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). 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 . This tectonics article is a stub. It moves Computed CMT depths in Table S1 in the Supporting Information range from 12 to 26 km, with 12 being the smallest constrained depth. "fault" or "fault line". R.P. Added to Thesaurus in 1989. Molnar They also calculated Mw for three earthquakes in 1969, 1971 and 1973; they and Molnar et al. We show in detail, however, that some segments of the three transforms are aseismic at the Mw > 5.4 level whereas others are more strongly coupled. Our knowledge of the Eltanin system is limited by the relatively high magnitude of completeness of events, Mw 5.4, and the paucity of aftershocks and forerunning events. Their 1000 km length is greater than that of any other oceanic transforms at fast-spreading plate boundaries. It is therefore unlikely that the event selection for 19902009 missed any earthquake with a moment magnitude greater than 5.5. We assume that earthquakes along a given segment of a transform occur on single faults although the distribution of CMT solutions scatters about 15 km perpendicular to the transforms. , and M is in kg. Figs 4-6 depict the three Eltanin transforms in greater detail. Dziewonski 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 Elevation map for localities Click for legend, zoom in for elevation lines Routing error m , | Map style: OpenTopoMap ( CC-BY-SA) 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. et al. 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. We find or confirm two anomalous characteristics: the . How that may vary along strike and affect seismic coupling is unknown. 2. Moment magnitudes are given below each solution. Unfortunately, the computed depths of earthquakes along the three Eltanin transforms are not accurate enough to ascertain centroid depths or the downdip width of seismic faulting at the several to 20 km level. (1993) attribute it to one of those small spreading centres. . That view was strengthen when Menard reviewed the manuscript and provided an unpublished bathymetric map that included more data in the far southeast Pacific. (2005), McGuire (2008) and Boettcher & McGuire (2009) find that some fault segments are characterized by a predominance of aseismic slip while others are fully coupled. (1993) find that a 10 clockwise rotation of magnetic anomalies north of the Heezen transform occurred within the last 4 Ma, which would put it in extension. They were generally too small to generate stable CMT results. 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. They differ in that hypocentres derived using body waves give the location of rupture initiation whereas CMT solutions give centroid locations and origin times. Distances in kilometres same as in Fig. 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? Gregg 2). Mw is systematically higher than mb for strike-slip events along the three transforms, on average about 0.5 units. If those segments are not fully coupled, our calculations of downdip width, of course, are minimum estimates. (PAR), immediately south of the Eltanin Fracture Zones (FZs). Who is Jason crabb mother and where is she? Their poorly determined repeat times range from 13 to 24 yr. 2006-01-01. Some parts of the Heezen and Tharp transforms exhibit strong seismic coupling but others were aseismic at the resolution of our study, Mw > 5.0-5.5. 6) indicates that it may be a single fault. Red triangle indicates CMT solution for shock of 1975 April 19. Fishing enthusiasts interested in fishing near or at Eltanin Fracture Zone System should print out the Google map and take it with them on their . The North Anatolian Fault is formed along the Anatolian plate What is the labour of cable stayed bridges? R.L. Shen Reported values for the ratios KlRb RblSr La/Yb and Sr87 86ISr for fresh material, generally'"hint at a We determined a few CMT mechanisms for which PDE or ISC did not compute hypocentres, for which we relied on detections and locations based on intermediate-period surface waves (Ekstram 2006). Shimazaki The continuity in smooth trend of the ridge and the Eltanin Fracture Zone suggests some relationship between them. 8) includes three events that are much larger than the others in that series. -Different segments of the mid-ocean ridge system spreading at different rates. 8) contains six events of Mw= 5.89 since 1971. -Different segments of the mid-ocean ridge system spreading at different rates. A.M. 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 . 2 shows the areal distribution of strike-slip earthquakes Mw > 5.5 as a function of their recomputed magnitude, Mw, in red along the three transform faults of the Eltanin system. Fracture Zone. 4706 km S of Papeete, French Polynesia / pop: 26,400 / local time: 01:42:15.1 2017-06-15 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. Their surface wave magnitudes, Ms, for events before 1969 along the Eltanin system were determined typically from one to a few stations. Publisher. 2. With that assumption we obtain downdip widths of about 5 km for four segments of the Heezen, Tharp and Hollister transforms. The time intervals again are well fit by the slip predictable model (dotted red line). Menard The segment of the Heezen transform between 29 and 71 km (Fig. The two largest (Mw 6.7 and 5.9) occurred well to the north of the transform in 2001 and 2007. Ms, which is typically reported by PDE and ISC only for Rayleigh waves and for periods between about 18 and 22 s, may yield a biased estimate of the long-period character of a seismic source as a result of low excitation at certain focal depths and biased sampling of the radiation field. The relationship between the two events that occurred on the same day with computed CMTs only 5 km apart is unknown. . The new results that include surface wave data are not very different from the earlier results. 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. His relocations along the Heezen transform, with one exception, are more tightly clustered than ours. M. Symbols, axes and origin of coordinates same as Fig. 6. We used a 97-km length of the Hollister that includes all large shocks (Fig. Johanson . The Udintsev Fracture Zone is a suitable site for a long-term monitoring of the Antarctic Circumpolar Current 1 Introduction The Antarctic Circumpolar Current (ACC) forms a continuous near-zonal band of eastward flow. His relocations are shown in Figs 4-6 in green. The inversion procedure follows the method of Ekstrm (1989) and leads to estimates of the earthquake focal mechanism, source-time function and point-source depth that are consistent with both the P-wave data and the CMT results. Challenger Fracture Zone. The experiment suggests that when the CMT depth is larger than the true depth, the estimated Mo is too high by a small amount. M.S. T2=42r3/(GM), m3/(kgs2)m ^ { 3 } / \left( k g \cdot s ^ { 2 } \right) Phipps Morgan Burgmann 4065 km S of Avarua, Cook Islands / pop: 13,373 / local time: 16:34:59.2 2016-05-02 The series includes two events of 6.17 and 6.18 and one of less certain Mw of 6.5 (Stewart & Okal 1983) on 1971 April 4 that are much larger than the other three. That may account for the variety of Mws along it. Enter your email address to follow this blog and receive notifications of new posts by email. C.J. west coast of the USA through California. A break in the smooth trend of the ridge at latitude 37.5S has been recognized in both bathymetric and altimetric data. Solutions for new earthquakes of Mw > 5.5 were not found after early 2002. To address part of this question, we performed the following experiment. Wilson (1965) utilized the observation that earthquakes along the Eltanin fracture zone were confined to the zone between two offset ridge crests in formulating his hypothesis of transform faulting. Their remoteness and rough seas, however, puts a premium on studying them at large distances using seismic waves and various satellite technologies. The centroids of events of larger Mw are found at least 35 km eastwards along the Heezen transform and those to its west are relatively small. Meteoritic Microfossils in Eltanin Impact Deposits. 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 . 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. Numbers for 15 yr period 1976-1990 were multiplied by 20/15. This attests to the very thin lithosphere at fast spreading ridges. 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. https://session.masteringgeology.com/problemAsset/3004355/4/MGEO_3004355_PartD.jpg. I.A. The ridge segments and transform faults of the East Pacific Rise and Pacific-Antarctic ridge are the sites of the fastest rates of the seafloor spreading and relative plate motion in the world. Our calculations for all events have the advantage of having been corrected for lateral heterogeneity with the same model. J.J. . Solomon The Romanche Fracture Zone offsets the Mid-Atlantic ridge by 900 km (560 mi), making it the largest equatorial fracture zone in the Atlantic. Searle 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. . A.B. The transform valley is 15-20 km wide and 2-4 km deep. 4699 km SW of Santiago, Chile / pop: 4,837,295 / local time: 15:09:44.3 2016-08-18 M. fracture zones and transform faults flashcards quizlet. A.M. 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. It is formed by a transform boundary. Fracture zone evolution is investigated using dynamic models that allow the fault zones to freely slip. 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). fault zone where the two blocks/plates on either side move side by 1975; Lonsdale 1994), which were named for M. Tharp, B. Heezen and C. Hollister (Fig. GE was partially supported by NSF grant EAR-09-24694. It is that region where three of the four normal faulting earthquakes in Fig. A.M. The smallest is likely to be an underestimate, since several patches within what we take to be the seismically active part of the Hollister transform were not active at the Mw= 5.9 level. Fig. 3315km (2060mi) WSW of Punta Arenas, Chile Watts 5 contains only two earthquakes of Mw 5.45 and 5.50. (2010) that describes the relative motion of the Pacific and Antarctic plates. A.M. which two plates create the eltanin fracture zone quizlet; Well Inspection using ROV at Kondashetti Halli, Bangalore Please see the related question for more information. We also used the same 3-D velocity model for our new CMT solutions. 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. Spreading Centre. 4. 3391km (2107mi) WSW of Ushuaia, Argentina E.A. A major purpose of our work is to examine the degree of repeatability (or lack thereof) of major earthquakes along various segments of the three Eltanin transforms. 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. M.D. 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. Woodward 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. Eltanin Fracture Zone. Their average repeat time is 7.1 yr and their COV is 0.28. 1975; Lonsdale 1994), which were named for M. Tharp, B. Heezen and C. Hollister . We did not use the ISC catalogue for events after 1999. The efforts that we made, which are described in Appendix A, resulted in a number of additional solutions, especially for the period 1976-1991 and for Mw 5.4-6.0 (see Fig. Okal Our new catalogue can be used in testing computer simulations of earthquake recurrence. 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. In detail the distribution of fault segments is likely to be fractal. 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). P. Earthquakes of Mw 6.2-6.4 have occurred repeatedly (Fig. 8, interaction between the two may well occur. As AABW flows through the Romanche Fracture Zone, salinity and temperature increase significantly. Bohnenstiehl et al. We take this along with the distributions of events in time and longitude after 1976 (Fig. 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. Oxford University Press is a department of the University of Oxford. Earthquakes were not found along nearby fast spreading ridges at that resolution. A.R. COV = 0 and 1.0 correspond to strict periodicity and random occurrence, respectively. [1] The two major faults in the Eltanin Fracture Zone are the Heezen Fault and the Tharp Fault. Richards, W.B.F. The zone is in the South . 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. Lonsdale (1994) concludes that a zone of extension north of the Heezen transform developed following a Pliocene change in relative plate motion. 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. . 4. -Linear spreading on Earth's curved surface. 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. The remaining five segments were the sites of fewer large shocks of Mw 6.0-6.39. T. Nine earthquakes from 1969 to 1975 are shown at their body wave locations of the International Seismological Centre (ISC). 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. The most recent data show, for example, that the Eltanin fracture zone system in the South Pacific is much longer than previously thought, according to Marsh. Wolfe et al. transform fault, in geology and oceanography, a type of fault in which two tectonic plates slide past one another. The segment of the Hollister transform between -635 and -650 km (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). 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. Test the following series for convergence or divergence. 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. . The segment between -210 and -241 km consists of a large number of events of Mw > 5.55, one of Mw 6.08, three of 6.15 =Mw= 6.17 and one of Mw 6.3 (Stewart & Okal 1983) on 1973 September 18. Hence, it and the two larger events occurred along an off-transform feature. The isobaths are drawn at 500 m intervals between 1900 and 3400 m, from the dataset of Smith and Sandwell (1995). The continuity in smooth trend of the ridge and the Eltanin Fracture Zone suggests some relationship between them. Marathon Expedition, Leg 6 Studies in the Tonga Trench, Louisville Ridge, and Eltanin Fracture Zone The San Andreas Fault zone of western North America. Other short spreading centres may exist along the Tharp and other parts of the Heezen transforms. Eltanin fracture zone Scope Notes: SE Pacific. The shaded area is the "Hollister region" whose seismicity is detailed in Fig. None of our normal-faulting solutions are found adjacent to that part of the Tharp transform. (2009). 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. 4. . Anderson The CMT methodology and format of the catalogue are described in Dziewonski (1981) and Ekstram (2005). Eltanin has a maritime climate in the transition region between the tundra and subarctic zones (Kppen classification) which is characterised by . Fox . ISC located an earthquake along that segment of Ms 6.1 on 1967 September 9. Fig. Boettcher 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. 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. Red and green symbols denote strike-slip faulting. florida a jurassic transform plate boundary. (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. Finally we are left with what accounts for transform segments that rupture with high seismic coupling and those with low coupling. 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. Antarctic Bottom Water (AABW) flows below the LNADW and reaches down to the seafloor. When Sykes showed his results to M. Ewing, the latter arranged with NSF (US National Science Foundation) for the Research Vessel Eltanin to map the region. Formed around Antarctica, the AABW is cold, has low salinity, and high silicate concentration. 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). This is a consequence of the continuity of displacement eigenfunctions for surface waves across discontinuities, and the dependence of the excitation on these displacements. The solutions, additional methodology and other pertinent data are described more fully in Appendix A and the Supporting Information. Watts et al. 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. What are mid-ocean ridges? (1997) for the intermediate-period, fundamental-mode surface waves. 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). Excluding it does not change the average repeat time for events of Mw > 5.9; it increases the SD and COV slightly. C.G. Distances in kilometres same as in Fig. This technique has the potential to rigorously assess hotspot fixity and to locate extinct hotspots. T.H. 1997, 2005). The San Andreas fault is part of a fault zone known as a transform transform plate boundaries learning geology. Menke 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. 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. Wolfe et al. 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. For the Eltanin events, this bias is unlikely to be larger than 15 per cent, even for the events with the deepest calculated centroids.

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