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Examine the figure above. 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 . Smith
. If the 1981 shock were mislocated at least 12 km eastwards, the length of the repeating segment would be about 30 km. Previously, some epicentral locations in that area were uncertain by as much as 500 km. How do you say Eltanin Fracture Zone? D.F. 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. where is and what is eltanin transform fault and fracture. Lin
2).
Y.
Topographic Map of 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. Pacific Ocean depth map showing the Heezen Fault and the Tharp Fault as #17. Computed CMT depths in Table S1 in the Supporting Information range from 12 to 26 km, with 12 being the smallest constrained depth. The transverse ridge separates the present trench from an 800km (500mi)-long aseismic valley where the Romanche transform was located until about 108 Ma. This yielded 84 earthquakes. Although magmatism was more or less continuous on the ridge during 28-60 Ma, it probably occurred on crust . Red and green symbols denote strike-slip faulting. (1993) obtained two normal-faulting mechanisms and computed depths of faulting from waveform matching. . 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. J.J.
Lonsdale (1994) concludes that a zone of extension north of the Heezen transform developed following a Pliocene change in relative plate motion. . They find that aftershock zones of nearby pairs of moderate-size earthquakes along fast-moving transforms were separated by small spreading centres. The eastern part of the transverse ridge, however, consists of a thick sequence of stratified material called the Romanche Sedimentary Sequence (RSS). 7 for events of Mw > 5.55 (blue) and Mw > 5.9 (red). The fault segment between -665 and -680 km (green symbols in Fig. 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. 4 and red symbols in Fig. Cumulative moment release is shown in Fig. The continuity in smooth trend of the ridge and the Eltanin Fracture Zone suggests some relationship between them.
4065 km S of Avarua, Cook Islands / pop: 13,373 / local time: 16:34:59.2 2016-05-02 We did not use the ISC catalogue for events after 1999. 1 for events of Mw 6.2 in 1983 and 2007. He found that interevent times for those pairs was tightly clustered around 5 yr with a COV ~ 0.2. In relocating earthquakes along the East Pacific Rise and Pacific-Antarctic Ridge, Sykes (1963) found that the pattern of epicentres was offset about 1000 km near 55 S. The four estimates of W in Table 1 range from 3.9 to 6.0 km. McGuire
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. Of the 84 earthquakes from 1976 to 1989, we rejected seven CMT solutions. J.
Which two plates create the Eltanin Fracture Zone? 7 are the best fit to that model. The precision of epicentral locations in his study was improved considerably by using data from new seismic stations in Antarctica that were installed during the International Geophysical Year, 1957-1958, and computer programs for analysing P and PKP arrival times. Data for the reanalysis were collected from all the main global digital networks that have operated since 1976. west coast of the USA through California. Hence, we cannot distinguish between those two models. Okal & Langenhorst (2000) relocated a number of earthquakes along the three transforms using short-period body waves. (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. [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. What are mid-ocean ridges? . 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. They are typified by some of the roughest sea conditions and most severe weather on the Earth. Their 1000 km length is greater than that of any other oceanic transforms at fast-spreading plate boundaries. This attests to the very thin lithosphere at fast spreading ridges. 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. L.R. Nevertheless, modelling body waves is difficult for strike-slip earthquakes along the Eltanin transforms because their amplitudes are small at recording stations that necessarily are at very large distances. His results support the idea that events along that segment break a single isolated asperity. The continuity in smooth trend of the ridge and the Eltanin Fracture Zone suggests some relationship between them. H.W. Ekstram
The principal fracture zones are identified, as are segments of the PAR. Reported values for the ratios KlRb RblSr La/Yb and Sr87 86ISr for fresh material, generally'"hint at a Bohnenstiehl
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. [2] However, the total offset is about 1600km. Most prominent is an asymmetric transverse ridge, at which abyssal hills adjacent to the fault zone have been . Individual ridge segments trend, how- ever, up to a few tens of degrees from the smooth trend. By chron 28 (63-64 Ma) about 750 km of the present 1000 km offset had accumulated across them. 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). Anderson
et al. F.
No known large earlier events can be readily attributed to the segment between 122 and 141 km in Fig. slip fault zone between the Caribbean and North American "zone" in Chinese : n. 1. () 2. 3. . Stewart
Abercrombie
Which letter is pointing to a transform fault? 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. With that assumption we obtain downdip widths of about 5 km for four segments of the Heezen, Tharp and Hollister transforms. Similarly, the series between 95 and 121 km (blue in Fig.
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. 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. . They found that all depths were less than 20 and a few better determined solutions were shallower than 5 km below the seafloor. Tolstoy
Those P waves left hypocentres close to the intersection of the two nodal planes (B-axis) where their amplitude is very small. 5 contains only two earthquakes of Mw 5.45 and 5.50. COV = 0 and 1.0 correspond to strict periodicity and random occurrence, respectively. 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. Cumulative seismic moment release for shocks of Mw > 5.55 from 1976 to 2010 along two segments of Hollister transform fault as indicated in Fig. 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. 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. These are very small, typically 3-15 km for the earliest events and 1-2 km for earthquakes since 2000.
[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. This is a much smaller difference than might have been anticipated from ratios of body-wave radiation amplitudes or other methods. Ryan
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 time intervals again are well fit by the slip predictable model (dotted red line). Aseismic parts of the Heezen and Tharp fracture zones can be traced far to the northwest and . 4. Figs 5 and 6 show five other normal-faulting mechanisms adjacent to but not on the Tharp and Hollister transforms. 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. Johanson
Eltanin fracture zone Scope Notes: SE Pacific. . It is the only example of a very short time interval between large shocks along segments of the Eltanin transforms. Behn
11 between Mw 5.4 and 6.0 for events from 1991 to 2010. This is a consequence of the continuity of displacement eigenfunctions for surface waves across discontinuities, and the dependence of the excitation on these displacements. Who is Jason crabb mother and where is she? . Fig. The smaller events in Fig. 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. E.A. Bergman
The relatively small size of that earthquake, its early date and the off-transform locations of other normal-faulting events lead us conclude it more likely occurred just north of the Heezen transform. 1975; Lonsdale 1994), which were named for M. Tharp, B. Heezen and C. Hollister (Fig. 8) includes three events that are much larger than the others in that series. 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. The relationship between the two events that occurred on the same day with computed CMTs only 5 km apart is unknown. trench to the Eltanin Fracture Zone. E.A. [3], The Romanche Fracture Zone offsets the Mid-Atlantic ridge by 900km (560mi), making it the largest equatorial fracture zone in the Atlantic. W.
(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. We obtained a CMT solution for an additional earthquake of Mw 6.15 in 1979. In contrast, normal-faulting events of Mw 5-6.5 are common along slower spreading ridges such as those in the Atlantic. 5) are characterized by shocks of Mw= 5.9 but about half of its length is not. (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. Added to Thesaurus in 1989. Excluding it does not change the average repeat time for events of Mw > 5.9; it increases the SD and COV slightly. Maternovskaya
Distances in kilometres same as in Fig. J.
P.
J.
Solomon
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. We first examine an unusual case of repeatability of shocks of nearly the same Mw, 6.0. The new result is well constrained by the surface wave data, which were not included in the original analysis. How are fracture zones like the Eltanin created? 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.
Distances: 4585 km SE of Wellington, New Zealand / pop: 382,000 / local time: 23:42:15.1 2017-06-15 His values and ours of COV = 0.26 imply quasi-periodic behaviour. The North Anatolian Fault is formed along the Anatolian plate 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 . The maximum size of earthquakes along fast spreading ridges themselves is not greater than magnitude 3 (McGuire 2008; M. Tolstoy, personal communication, 2010). 3292km (2046mi) WSW of Puerto Natales, Chile Wolfe et al. 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. Cumulative seismic moment release for shocks of Mw > 5.55 from 1969 to 2010 along three additional segments of Heezen transform fault as indicated in Fig. Tromp
A break in the smooth trend of the ridge at latitude 37.5S has been recognized in both bathymetric and altimetric data.
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. 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. Forsyth
We report the unique occurren Gregg
Deep water flow through the trench is from west to east with a rate of 3.6 Sverdrups (million m/s) of 1.57C (34.83F) water. This is an improvement over past formulations where bathymetric offsets were imposed kinematica. As it flows north, it is constrained by numerous obstacles on the seafloor. 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. The central part of the Tharp transform near -350 km in Fig. Phipps Morgan & Forsyth (1988), Shen & Forsyth (1992), Behn (2007), Gregg et al. (2009). K.
ISC located an earthquake along that segment of Ms 6.1 on 1967 September 9. Wolfe et al. S. Carbotte kindly computed the bathymetric map in Fig. Observed P waves for a normal-faulting event, however, leave close to their maximum radiation on the focal sphere. Listen to the audio pronunciation of Eltanin Fracture Zone on pronouncekiwi
Argus
E.J.
Other short spreading centres may exist along the Tharp and other parts of the Heezen transforms. 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. 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 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 The zone is in the South . At 14.5W the trough reaches a maximum depth of 2895 fm (5470 m). (2010) that describes the relative motion of the Pacific and Antarctic plates. 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. J.J.
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). Since that segment is adjacent to the one in blue in Fig. J.K.
. That view was strengthen when Menard reviewed the manuscript and provided an unpublished bathymetric map that included more data in the far southeast Pacific. C.J. . S.M. Moment magnitudes are given below each solution. S. Carbotte (written communication, 2011 July 22) notes, however, that some of the shocks along the eastern end of the Tharp transform might fall within a zone of deformed/rotated seafloor south of the transform that looks quite similar to the zone of deformation north of the Heezen transform described by Lonsdale (1994) and seen in Fig. The normal-faulting event of 2001 August 6 is larger than that of any of the strike-slip events along the three Eltanin transforms. 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. Wolfe et al. That may account for the variety of Mws along it.
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.
(1975) obtained strike-slip mechanisms for them and another event in 1967. 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 . It bisects the Mid-Atlantic Ridge (MAR) just north of the equator at the narrowest part of the Atlantic between Brazil and West Africa, extending from 2N to 2S and from 16W to 20W. Bathymetry from Ryan et al. What kind of fault is represented by the eltanin and romanche fracture zones? However, a major offset developed on this transform between 60 and 80 Ma, prior to the oldest dated rocks from the ridge. Symbols, axes and origin of coordinates same as Fig. (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. Thermal models with constant and variable mineral physics properties are formally analyzed for fits against recently filtered databases for heat flow and topography.