The mechanism in the GCMT catalogue indicates normal faulting, while the reanalysis resulted in a strike-slip mechanism. 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. The segment of the Hollister transform between -635 and -650 km (Fig. Challenger Fracture Zone. To address part of this question, we performed the following experiment. 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. 7, however, since it is located just to the east of other large shocks along the Heezen transform. 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. Ekstram What is the answer punchline algebra 15.1 why dose a chicken coop have only two doors? 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. T.H. 2. The Romanche and Chain Fracture Zones creates a huge gap in the MAR and can act as a "Subsea Berlin Wall" segregating the North Atlantic communities from those in other oceans. Meteoritic Microfossils in Eltanin Impact Deposits. Fielding 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. Moment release in earthquakes of Mw= 6.08 is about 60 per cent of that for Mw > 5.55. Oxford University Press is a department of the University of Oxford. [2] However, the total offset is about 1600km. These segments contain fewer events of Mw > 5.9 than that in Fig. (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. The San Andreas fault is part of a fault zone known as a transform Eltanin has a maritime climate in the transition region between the tundra and subarctic zones (Kppen classification) which is characterised by . 7, many of the smaller events are either aftershocks or foreshocks and are considered to be noise for the purposes of assessing the repeat times of the largest earthquakes. Chou This is an improvement over past formulations where bathymetric offsets were imposed kinematica. Anderson Boettcher The new result is well constrained by the surface wave data, which were not included in the original analysis. Ekstram Phipps Morgan This translates into a lack of sensitivity of the CMT algorithm in the estimation of the centroid depth, and instances in which the centroid depth differs appreciably from the true depth of the earthquake, here considered the centre of seismic moment. 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. Tromp transform plate boundaries learning geology. [1] The two major faults in the Eltanin Fracture Zone are the Heezen Fault and the Tharp Fault. By chron 28 (63-64 Ma) about 750 km of the present 1000 km offset had accumulated across them. 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 Wolfe et al. D.W. We used a box from 54S to 58S and 140W to 120W to identify earthquakes that might be located on the Eltanin transform system. F. 7 for events of Mw > 5.55 (blue) and Mw > 5.9 (red). The present application of this method points to a recent change in Pacific plate motion, and. 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. The Romanche Fracture Zone offsets the Mid-Atlantic ridge by 900 km (560 mi), making it the largest equatorial fracture zone in the Atlantic. COV = 0 and 1.0 correspond to strict periodicity and random occurrence, respectively. Similarly, the series between 95 and 121 km (blue in Fig. 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. The fracture along blocks of crust (tectonic plates) is called a of fracture zones in the southern oceans by mavis lynn driscoll b.a., university of california at berkeley, 1981 submitted in partial fulfillment of the requirements for the degree of doctor of philosophy at the massachusetts institute of technology and the woods hole oceanographic institution june 1987 Okal Log of cumulative number of earthquakes per 20 yr larger than a given Mw as a function of Mw. [3], Series of faults that offset the Pacific-Antarctic Ridge. T.A. The segment of the Heezen transform between 29 and 71 km (Fig. It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide, This PDF is available to Subscribers Only. 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. Wolfe et al. 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. Data for the reanalysis were collected from all the main global digital networks that have operated since 1976. 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. This completeness can be seen as well by the slope of 1.0 of the LogNMw relationship in Fig. S. Carbotte kindly computed the bathymetric map in Fig. 4065 km S of Avarua, Cook Islands / pop: 13,373 / local time: 16:34:59.2 2016-05-02 Solid line indicates Mw=Ms. Lonsdale E.A. The zone is in the South . Wolfe et al. (1975) obtained strike-slip mechanisms for them and another event in 1967. This is a much smaller difference than might have been anticipated from ratios of body-wave radiation amplitudes or other methods. The maximum size of earthquakes along fast spreading ridges themselves is not greater than magnitude 3 (McGuire 2008; M. Tolstoy, personal communication, 2010). Which letter is pointing to a transform fault? A fault is a fracture in the rocks where movement occurs. R. Mammericks 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. Map view of CMT locations of earthquakes along Tharp transform from 1976 to 2010. Our distributions of earthquakes do not fit other thermal models that we have examined. 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. (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. J.J. Johanson (2009). Eltanin Fracture Zone System is located in the Undersea Features Area of the Country of Undersea Features. Lin 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. Cumulative moment release along that segment is displayed in Fig. 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 Romanche Trench, also called the Romanche Furrow or Romanche Gap, is the third deepest of the major trenches of the Atlantic Ocean, after the Puerto Rico Trench and the South Sandwich Trench. 3) along the eastern part of the Heezen transform between +100 and +200 km (Fig. The earthquakes were analysed using the standard Global CMT (GCMT) algorithm as described in Dziewonski et al. The remaining five segments were the sites of fewer large shocks of Mw 6.0-6.39. The T-axis of a normal-faulting event in that area of Mw 5.4 in 1978 is inclined about 45 to the transform (Fig. It is therefore unlikely that the event selection for 19902009 missed any earthquake with a moment magnitude greater than 5.5. The North Anatolian Fault is formed along the Anatolian plate 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. [4] Enter the email address you signed up with and we'll email you a reset link. Previously, some epicentral locations in that area were uncertain by as much as 500 km. 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 N.N. 4, between -25 km and 0 km). "fault" or "fault line". 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. A.B. 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. If we assume that all of the true depths of these earthquakes are shallow, what size error or bias should we expect in estimates of Mo? Strike-slip mechanism in centre is that for 2007 event. We refer to the magnitudes derived from those moment tensors as either new or recomputed Mws. How are fracture zones like the Eltanin created? Distances along the transform are calculated from an arbitrary origin of coordinates at 55.4 S, 125.0 W. 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 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. (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. 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. Neither Okal & Langenhorst (2000) nor we found any normal faulting earthquakes along spreading ridges adjacent to the Eltanin fault system. A.M. We find or confirm two anomalous characteristics: the . Publisher. 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. 4). 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. Burgmann 2. 4 are more tightly clustered in map view. The smooth trend of the ridge is NNW-SSE with a trend break at about 37.8S. 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. Our calculations of moment magnitude Mw are compared with determinations of the short-period magnitude mb in Fig. What is error code E01-5 on Toyota forklift. 1997, 2005). 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. (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. 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). In this paper we concentrate on these phenomena using earthquakes that have been relocated and reanalysed using long-period digital data from global stations for a recent 35-yr period (Fig. His events along what we identify as a well-coupled zone between 29 and 59 km in Fig. 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. None of the five is reasonably attributed to a small spreading segment along either of those two transforms. . , and M is in kg. FRACTURE ZONE. . M. Aseismic parts of the Heezen and Tharp fracture zones can be traced far to the northwest and . M.D. CHALLENGER FRACTURE ZONE. M. The horizontal axis is parallel to computed transform directions; the vertical is perpendicular to it. We also used the same 3-D velocity model for our new CMT solutions. 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 ) D.F. Their poorly determined repeat times range from 13 to 24 yr. 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 . J. 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. The Eltanin Transform Fault and Fracture Zone is a series of six or seven dextral transform faults along ~800 km of the. The transform valley is 15-20 km wide and 2-4 km deep. Dotted lines denote approximate locations of ridge segments. For LNADW and AABW, the Romanche and Chain Fracture Zones (just south of the equator) are the only deep passages in the MAR where interbasin exchange is possible. Fracture zone evolution is investigated using dynamic models that allow the fault zones to freely slip. 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 Extending the work of Stewart & Okal (1983), they again emphasized the dominance of aseismic slip. . Red and green symbols denote strike-slip faulting. Marathon Expedition, Leg 6 Studies in the Tonga Trench, Louisville Ridge, and Eltanin Fracture Zone The relationship between the two events that occurred on the same day with computed CMTs only 5 km apart is unknown. Dziak A large iceberg interfered with one scientific mapping (Lonsdale 1994). Enter your email address to follow this blog and receive notifications of new posts by email. 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). 8) contains six events of Mw= 5.89 since 1971. The average repeat time for the eight events of Mw > 5.9 is 4.0 1.0 (1 SD) yr. 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. M.S. It moves However, a major offset developed on this transform between 60 and 80 Ma, prior to the oldest dated rocks from the ridge. These are too small to represent the actual uncertainties. 2006-01-01. McGuire Broader Terms: East Pacific Pacific Ocean South Pacific Southeast Pacific T. If those short spreading centres are very young, they may not have had enough time to become oriented perpendicular to the transform. 4 and red symbols in Fig. (1993) for two other normal faulting earthquakes off the Eltanin transforms. . Surface waves have an advantage for precise locations over body waves since their velocity is much less. 2). Their average repeat time is 7.1 yr and their COV is 0.28. Fig. 1999). m3/(kgs2). The Polar and Subantarctic Fronts are observed to pass along the Udinstev Fracture Zone 3 as the jets in the flow are steered by the topography (e.g., Moore et al. 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. transform faults fracture zones and the kinematics of. Indeed, jets are observed to pass along both the Udinstev and Eltanin Fracture Zones (Gille 1994; Hughes and Ash 2001). 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. Where is and what is Eltanin Transform Fault and Fracture Zone? -Different segments of the mid-ocean ridge system spreading at different rates. Search for other works by this author on: Earthquake slip on oceanic transform faults, Global CMT analysis of moderate earthquakes, Mw He concluded that a major fracture zone intersected the mid-oceanic ridge at that location, much like those mapped by Menard (1960) farther north. For example, the caridean shrimp Alvinocaris muricola inhabits cold seeps in both the Gulf of Mexico and the Gulf of Guinea, which clearly suggests a gene flow across the Atlantic, but the amount of data is very limited and dispersal pathways are not fully understood. The segment of the Heezen from 179 to 200 km has the next smallest T, 7.1 yr, Mw 5.89-6.5 and six events. Spreading Centre. 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. 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. Y. . The combined three Eltanin transform faults are much more active at the Mw~ 6 level than a comparable length of either the San Andreas Fault in California or other transform systems on land. We also analysed the P waves of the two largest normal-faulting events, those of 2001 and 2007 (Fig. Larson 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. How that may vary along strike and affect seismic coupling is unknown. 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. 1). 3). Hence, we suspect that the events at the western end of the Tharp transform are anomalous in some sense. The continuity in smooth trend of the ridge and the Eltanin Fracture Zone suggests some relationship between them. Bivalve communities have been reported around vents further south. They proposed that the Eltanin transforms consisted of small, well-separated asperities that rupture in earthquakes. . 4. 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. Solomon (1993) and Lonsdale (1994) describe three short spreading centres with a total length of about 6 km along the seismically quiet part of the Heezen transform between 125.5 and 126 W (Fig. 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. Wolfe et al. How are fracture zones like the Eltanin created? Numbers for 15 yr period 1976-1990 were multiplied by 20/15. GE was partially supported by NSF grant EAR-09-24694. C1. Gee Cumulative seismic moment release from 1976 to 2010 along a 42-km section of Heezen transform indicated in Fig. This is a consequence of the continuity of displacement eigenfunctions for surface waves across discontinuities, and the dependence of the excitation on these displacements. Hence, we cannot distinguish between those two models. 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. 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. A.R. Searle Distances in kilometres same as in Fig. The western part of the transverse ridge consists of fragments of uplifted oceanic crust and upper mantle. That Ms was obtained using a single station. We propose that the remainder of the plate motion . 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. That view comes in large part from assuming that the downdip (vertical) width of seismic faulting extends to about the 600 C isotherm as calculated using simple conductive plate cooling models where temperature at a given location along the transform is taken as the average on its two sides. (1993) obtained two normal-faulting mechanisms and computed depths of faulting from waveform matching. 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 few involving normal faulting are located up to 40 km on either side of the transforms and involve extension nearly normal to the transforms. 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. The centroid epicentre and time did not shift appreciably in these different inversions, nor did the geometry of the moment tensor change appreciably. 4. 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 occurred. 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. Available long-period data for events along the three transforms increased from about 15 to 100 global stations as illustrated in Fig. Kent Mw determined in this study compared with short-period body-wave magnitude mb as computed by either ISC or PDE. Since CMT locations are not available before 1976, the 10 largest earthquakes from 1969 to 1975 are shown in green at their body-wave locations of the International Seismological Centre (ISC). 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. 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. 7. E.J. We find that seismic coupling is not merely a function of relative plate velocity, location along the transform and transform length. Maternovskaya Forsyth (1993) found another normal faulting event just to the south of the Menard transform fault at 49.5 S along the same plate boundary. Stewart & Okal (1983) modelled P and reflected body waves for several strike-slip events along the Eltanin system. 4), to constrain their source depths. Bohnenstiehl This attests to the very thin lithosphere at fast spreading ridges. The normal-faulting event of 2001 August 6 is larger than that of any of the strike-slip events along the three Eltanin transforms. This section appears to be separated from the western basin of the Atlantic by a sill of 4500 m (2400 fm) near 17W. 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). 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'. 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. J. Symbols, axes and origin of coordinates same as Fig. -Linear spreading on Earth's curved surface. None of our normal-faulting solutions are found adjacent to that part of the Tharp transform. Sedimentary rocks consist of particles derived from the weathering of other from EARTH SCIE 213 at IIT Kanpur Their remoteness and rough seas, however, puts a premium on studying them at large distances using seismic waves and various satellite technologies. They differ in that hypocentres derived using body waves give the location of rupture initiation whereas CMT solutions give centroid locations and origin times. (PAR), immediately south of the Eltanin Fracture Zones (FZs). The Fracture Zone is located at the latitude and longitude coordinates of -54 and -130. 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. Bohnenstiehl et al. Ekstram stand on one side of it, the other side appears to move to the The summit of the transverse ridge is capped by Miocene shallow water limestones that reached above sea level 20 Ma before subsiding abnormally fast. 7; several were the sites of two or three earthquakes of Mw > 6.15. . The island is very long and narrow. Is the singer Avant and R Kelly brothers? Several of those well-coupled segments ruptured quasi-periodically in earthquakes of Mw~5.5-6 and with repeat times shorter than 10 yr. We choose the Eltanin transform faults as another good place to search for these phenomena. They concluded from analyses of seismograms, however, that the transform earthquakes themselves did not have a significant component of slow seismic slip. The eastern part of the transverse ridge, however, consists of a thick sequence of stratified material called the Romanche Sedimentary Sequence (RSS). S.C. LOUISVILLE RIDGE AND ELTANIN FRACTURE ZONE 3053 west to isolated peaks superimposed on ridge segments in the southeast. We conclude that strike-slip and normal faulting along the three Eltanin transforms are partitioned so that strike-slip faulting takes place along the transforms themselves and normal faulting occurs nearby but just off the transforms. Solutions for new earthquakes of Mw > 5.5 were not found after early 2002. (2002) used nearby hydroacoustic stations to locate very small events and aftershocks along a number of oceanic transform faults. Added to Thesaurus in 1989. (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. . 4. 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 .