Origin of the Louisville Ridge and its relationship to the Eltanin 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 A single strike-slip event of Mw 5.15 was obtained along a long section of the western part of the Heezen transform between -110 and +10 km. This tectonics article is a stub. (1975) obtained strike-slip mechanisms for them and another event in 1967. We also used the same 3-D velocity model for our new CMT solutions. Numbers for 15 yr period 1976-1990 were multiplied by 20/15. Earth Extremities 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 . This term has multiple hierarchies. Search for: Recent Posts. 10.17882/59800. 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. 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. As AABW flows through the Romanche Fracture Zone, salinity and temperature increase significantly. Smith 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. A.M. According to the normal scenario for the opening of the South Atlantic, it is spreading at a rate of 1.75 cm/year (0.69 in/year) and began forming about 50 Ma. Where is and what is Eltanin Transform Fault and Fracture Zone? 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. (2009). That segment may well not be a single isolated an asperity as that in Fig. west coast of the USA through California. Unlike all the other countries in the St. Cecilia Archipelago, Eltanin is only comprised of one island. 7 for events of Mw > 5.55 (blue) and Mw > 5.9 (red). The island is very long and narrow. Aseismic parts of the Heezen and Tharp fracture zones can be traced far to the northwest and southeast. 6. J.K. Posts about Eltanin Fracture Zone System written by yamkin. Recurrence of events along nearly the same fault segment is much more difficult to determine for transform faults on land, such as the San Andreas, where large to great earthquakes typically have repeat times of 100 yr or longer and instrumental data and exact dates for more than one earthquake along a fault segment are rare or non-existent. 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. What Is A Fracture Zone - Realonomics M.S. McGuire The central part of the Tharp transform near -350 km in Fig. Surface waves have an advantage for precise locations over body waves since their velocity is much less. Earthquakes along Eltanin transform system, SE Pacific Ocean: fault The maximum size of earthquakes along fast spreading ridges themselves is not greater than magnitude 3 (McGuire 2008; M. Tolstoy, personal communication, 2010). 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 . www.science.gov We first examine an unusual case of repeatability of shocks of nearly the same Mw, 6.0. Depths modelled by Wolfe et al. . Johanson Cumulative moment release is shown in Fig. The total length of the three en echelon faults is nearly 1000 km; each is characterized by fast long-term rates of displacement of about 80 mm yr-1. . 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. . 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. Their surface wave magnitudes, Ms, for events before 1969 along the Eltanin system were determined typically from one to a few stations. We note that our revised catalogue with its additions of more solutions, especially of Mw 5.5-6.0, is more complete than the existing CMT catalogue. In detailed swath mapping of three ultra fast-moving transforms just to the south of the equator, Searle (1983) found that each consisted of two or more short transforms bounded by very short spreading centres. Bar at upper right on map shows water depths in metres. For the period 19902009, we rejected only one event, which occurred on 2001 August 6. Wolfe et al. We choose to use a greater number of stations as time proceeded rather than use a few common stations as he did. M.S. Test the following series for convergence or divergence. Lonsdale (1994) concludes that a zone of extension north of the Heezen transform developed following a Pliocene change in relative plate motion. We then examine other segments with fewer but larger earthquakes. Dziewonski et al. . D.R. The point-source depths are about 10-12 km, which suggests that the earthquakes ruptured faults that cross the M discontinuity. The CMT centroid depths for events along the Eltanin system are not accurate enough to define the depths or range of seismic faulting at the level of several to 20 km. Others related faults include the Vacquier Transform Fault, the Menard Transform Fault, and the Udintsev Fault.[3]. 4699 km SW of Santiago, Chile / pop: 4,837,295 / local time: 15:09:44.3 2016-08-18 Best-fitting linear relationships are drawn through the dates of earthquakes and the seismic moment that had just been accumulated. 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. Seismic properties of the Eltanin Transform System, South Pacific The fracture along blocks of crust (tectonic plates) is called a Ryan Menard M.D. . 5) are characterized by shocks of Mw= 5.9 but about half of its length is not. Age- and sex-specific incidence of femoral neck and - PubMed 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. Most prominent is an asymmetric transverse ridge, at which abyssal hills adjacent to the fault zone have been . Note exaggerated scale in transform-perpendicular direction. The trench has been formed by the actions of the Romanche Fracture Zone, a portion of which is an active transform boundary offsetting sections of the Mid-Atlantic Ridge. 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). You can help Wikipedia by expanding it. Anderson PDF WI - Massachusetts Institute of Technology What did the Nazis begin using gas chambers instead of mobile killing units and shooting squads after a while? Dredged volcanic rocks from the southern oceans: the Eltanin collection M.D. 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. L.M. 11 for Mw > 6. D.F. Okal 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. Eltanin is an island located in the South Pacific Ocean, following the contours of the Eltanin Fracture Zone. 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. Examine the figure above. At least one seamount chain, the New England Seamounts, lies in the northwestern Atlantic. We propose that the remainder of the plate motion . plates. Argus Origin of the Louisville Ridge and its relationship to the Eltanin We find that one isolated asperity along the Heezen transform ruptures about every 4.0 1.0 yr. The transform valley is 15-20 km wide and 2-4 km deep. This shock of mb 5.6 in the PDE catalogue occurred only 4 min after the Mw 6.7 normal-faulting event near the Heezen transform, and the waveforms are not sufficiently separated to make a CMT analysis possible. H.W. 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 . How that may vary along strike and affect seismic coupling is unknown. 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. Figs 5 and 6 show five other normal-faulting mechanisms adjacent to but not on the Tharp and Hollister transforms. There are about 300 fracture zones, with an average north-south separation of 55 kilometres (34 mi): two for each degree of latitude. The steep slope of about -2.9 for Mw > 6 is unusual. Reported values for the ratios KlRb RblSr La/Yb and Sr87 86ISr for fresh material, generally'"hint at a S1 in the Supporting Information). 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. 4 and red symbols in Fig. Undersea Features Fishing & Outdoor Fracture Zone Maps: Undersea Features is home to a total of 187 Fracture Zone(s), listed below. Sedimentary rocks consist of particles derived from Events of Mw > 5.9 account for 70 per cent of the moment in Fig. Wolfe et al. All of them occurred along the parts of the transforms that were most active from 1976 to 2010. It seems unlikely that our CMT location errors would change much over the length of the Tharp transform. Origin of the Louisville Ridge and its relationship to the Eltanin 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 . Similarly, the series between 95 and 121 km (blue in Fig. (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. They find that aftershock zones of nearby pairs of moderate-size earthquakes along fast-moving transforms were separated by small spreading centres. 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. A transform fault may occur in the portion We refer to the magnitudes derived from those moment tensors as either new or recomputed Mws. GE was partially supported by NSF grant EAR-09-24694. Computed CMT depths in Table S1 in the Supporting Information range from 12 to 26 km, with 12 being the smallest constrained depth. 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. G. Their 1000 km length is greater than that of any other oceanic transforms at fast-spreading plate boundaries. The San Andreas Fault zone of western North America. Louisville chain has been related to the Eltanin fracture zone in several models (Hayes and Ewing, 1971;Larson and Chase, 1972;Watts et al., 1988). m3/(kgs2). Ekstram This is not surprising since all stations are at large teleseismic distances. Where is and what is Eltanin Transform Fault and Fracture Zone? S. Carbotte kindly computed the bathymetric map in Fig. 2006). P. 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). The 40Ar39Ar dating of rocks dredged . Sunrise, sunset, day length and solar time for Stockholm County. 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. What kind of fault is represented by the eltanin and romanche fracture [2] However, the total offset is about 1600km. W.B.F. . Eltanin Fracture Zone on the Elevation Map. 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 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 Plateand the Antarctic Plate. D.L. If those segments are not fully coupled, our calculations of downdip width, of course, are minimum estimates. Moment release in earthquakes of Mw= 6.08 is about 60 per cent of that for Mw > 5.55. 4706 km S of Papeete, French Polynesia / pop: 26,400 / local time: 01:42:15.1 2017-06-15 We interpret it as indicative that only some parts of the three Eltanin transforms are capable of generating shocks of Mw 6.1-6.4 and that events much larger than 6.4, especially events of Mw > 7, are unlikely to occur. S.M. McGuire The average repeat time for the eight events of Mw > 5.9 is 4.0 1.0 (1 SD) yr. We obtained a CMT solution for an additional earthquake of Mw 6.15 in 1979. List of fracture zones | Detailed Pedia We find one segment of the Heezen transform has ruptured quasi-periodically since 1976 in eight shocks of Mw 5.9-6.1 with an average repeat time of 4 yr. We recomputed centroid moment tensor (CMT) solutions for 190 earthquakes along and close to the three transforms of the Eltanin system from 1976 to 2010. R. What is the labour of cable stayed bridges? 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 '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. Is the singer Avant and R Kelly brothers? The feature was then named the Eltanin fracture zone. [3], The Romanche Fracture Zone offsets the Mid-Atlantic ridge by 900km (560mi), making it the largest equatorial fracture zone in the Atlantic. 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. Eltanin fracture zone_Eltanin fracture zone_ Dziewonski Nakata 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. On this Wikipedia the language links are at the top of the page across from the article title. E.A. Eltanin fracture zone Scope Notes: SE Pacific. Eltanin Fracture Zone. Gregg [1], It was named after the French navy ship La Romanche, commanded by captain Louis-Ferdinand Martial which on 11 October 1883 made soundings that revealed the trench. [3], Series of faults that offset the Pacific-Antarctic Ridge. 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. (1981), Arvidsson & Ekstrm (1998) and Ekstrm et al. The presence of short intratransform spreading segments is one factor but others may be differences in hydrothermal alteration and rock type, the sizes of asperities and varying normal stresses and fluid pressures that may place some segments in the velocity strengthening regime and others in the velocity weakening regime. Eltanin Fracture Zone System - myfishmaps.com 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 . According to the normal scenario for the opening of the South Atlantic, it is spreading at a rate of 1.75cm/year (0.69in/year) and began forming about 50 Ma. Solutions for new earthquakes of Mw > 5.5 were not found after early 2002. (2010) that describes the relative motion of the Pacific and Antarctic plates. Seismicity and aseismic slip along the Eltanin Fracture Zone Gordon They proposed that the Eltanin transforms consisted of small, well-separated asperities that rupture in earthquakes. Gee Indeed, jets are observed to pass along both the Udinstev and Eltanin Fracture Zones (Gille 1994; Hughes and Ash 2001). Bohnenstiehl et al. florida a jurassic transform plate boundary. None of our normal-faulting solutions are found adjacent to that part of the Tharp transform. This section appears to be separated from the western basin of the Atlantic by a sill of 4500 m (2400 fm) near 17W. The horizontal axis is parallel to computed transform directions; the vertical is perpendicular to it. Tectonic and magmatic ridges in the eltanin fault system - SpringerLink In the basin on the eastern side of the MAR the Walvis Ridge blocks the northward passage. Montesi J.J. Stewart & Okal (1983) modelled P and reflected body waves for several strike-slip events along the Eltanin system. L.R. The new CMT catalogue that we obtained is more complete than older versions. 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. 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. 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. Abercrombie , and M is in kg. Y. He attributed this to changes in the Euler pole for Pacific-Nasca plate motion during the last several million years. 7, several of which are aftershocks and foreshocks, are considered to be noise in ascertaining the quasi-periodic behaviour of the larger shocks. [1], Lower North Atlantic Deep Water (LNADW) is found around 3,6004,000 metres (11,80013,100ft) below sea level and flows from the Greenland and Norwegian seas; it brings high salinity, oxygen, and freon concentrations towards the equator. stand on one side of it, the other side appears to move to the 4. Structural geomorphology of the eltanin fault system and adjacent Symbols, axes and origin of coordinates same as Fig. The data since 1969 and those of Stewart & Okal (1983) for events back to 1920 indicate that earthquakes of Mw > 7 have not ruptured very long segments of any of the transforms. How To Pronounce Eltanin Fracture Zone: Eltanin Fracture Zone pronunciation We find or confirm two anomalous characteristics: the . Menard The Fracture Zone is located at the latitude and longitude coordinates of -54 and -130. New Mw corresponds to seismic moment magnitude recomputed for this study. 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. 2006-01-01. slip fault zone between the Caribbean and North American Knowledge gained from them and other oceanic transform faults may aid in understanding the long-term behaviour of transform faults on land and those at subduction zones where large-to-great earthquakes recur with repeat times of 100 yr or more. Distances along the transform are calculated from an arbitrary origin of coordinates at 55.4 S, 125.0 W. 8, interaction between the two may well occur. Eltanin has a maritime climate in the transition region between the tundra and subarctic zones (Kppen classification) which is characterised by . The remaining five segments were the sites of fewer large shocks of Mw 6.0-6.39. 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. Major differences in seismic coupling along strike are not in accord with common thermal models of plate cooling but instead are attributed to varying degrees of metamorphism, rock type and effective normal stress and possibly to the presence of short intratransform spreading centres. Ekstram Approximate slopes are denoted by dashed lines. transform fault, in geology and oceanography, a type of fault in which two tectonic plates slide past one another. With that assumption we obtain downdip widths of about 5 km for four segments of the Heezen, Tharp and Hollister transforms.
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