Hence, a variety of rupture behaviours, repeat times and maximum observed magnitudes is associated with the active parts of the three transforms. 4. Archived seismicity, satellite altimetry, and older geophysical traverses extend these descriptions . None of our normal-faulting solutions are found adjacent to that part of the Tharp transform. If the 1981 shock were mislocated at least 12 km eastwards, the length of the repeating segment would be about 30 km. The two largest (Mw 6.7 and 5.9) occurred well to the north of the transform in 2001 and 2007. Bohnenstiehl They proposed that the Eltanin transforms consisted of small, well-separated asperities that rupture in earthquakes. Cumulative moment release along that segment is displayed in Fig. 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. C.J. Abercrombie E.A. Most prominent is an asymmetric transverse ridge, at which abyssal hills adjacent to the fault zone have been . Stewart & Okal (1983) modelled P and reflected body waves for several strike-slip events along the Eltanin system. This bias suggests that the models used for CMT and ISC locations are not slow enough to the north and northeast along the East Pacific Rise. The present application of this method points to a recent change in Pacific plate motion, and. 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. 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. The morphology of the Atlantis Fracture Zone is typical of that of slow-slipping transforms. Behn The zone is in the South . . 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 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. 4699 km SW of Santiago, Chile / pop: 4,837,295 / local time: 15:09:44.3 2016-08-18 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 D.W. Map view of CMT locations of earthquakes along Tharp transform from 1976 to 2010. A.M. - 4:5, using intermediate-period surface waves, Thermal structure of oceanic transform faults, Scaling relations for seismic cycles on mid-ocean ridge transform faults, Aftershock sequences in the mid-ocean ridge environment: an analysis using hydroacoustic data, Determination of earthquake source parameters from waveform data for studies of global and regional seismicity, A very broad band inversion method for the recovery of earthquake source parameters, Global detection and location of seismic sources using surface waves, Measurements and global models of surface wave propagation, Global seismicity of 2003: centroid-moment-tensor solutions for 1087 earthquakes, Source of oceanic magnetic anomalies and geomagnetic polarity time scale, Spreading rate dependence of gravity anomalies along oceanic transform faults, Co-seismic and postseismic slip of the 2004 Parkfield earthquake from space-geodetic data, Structural geomorphology of the Eltanin fault system and adjacent transform faults of the Pacific-Antarctic plate boundary, Seismic cycles and earthquake predictability on east Pacific rise transform faults, Foreshock sequences and short-term earthquake predictability on east Pacific rise transform faults, Magnetic anomalies, bathymetry and the tectonic evolution of the South Pacific since the Late Cretaceous, Three-dimensional flow and temperature perturbations due to a transform offset, Seismic properties of the Eltanin transform system, South Pacific, Global multi-resolution topography synthesis, Multiple, closely spaced transform faults in fast-slipping fracture zones, The effects of temperature and pressure-dependent viscosity on three-dimensional passive flow of the mantle beneath a ridge-transform system, Time-predictable recurrence model for large earthquakes, Seismicity and aseismic slip along the Eltanin fracture zone, Repeat times of large earthquakes: implications for earthquake mechanics and long-term prediction, Moderate and large earthquake activity along oceanic transform faults, Origin of the Louisville ridge and its relationship to the Eltanin fracture zone system, A new class of faults and their bearing on continental drift, Oceanic transform earthquakes with unusual mechanism or locations: relation to fault geometry and state of stress in the adjacent lithosphere, The Authors Geophysical Journal International 2011 RAS, Fault identification and reliability evaluation using an SVM model based on 3D seismic data volume, Surface waves at a fluid/double-porosity medium interface, Adjoint-state traveltime tomography for azimuthally anisotropic media in spherical coordinates, Defining the Yangtze-Cathaysia suture zone in south china using ambient noise tomography, Observations and simulations of the meteotsunami generated by the Tonga eruption on 15 January 2022 in the Mediterranean Sea, Volume 234, Issue 1, July 2023 (In Progress), Volume 233, Issue 3, June 2023 (In Progress), Volume 233, Issue 2, May 2023 (In Progress), Volume 233, Issue 1, April 2023 (In Progress), Geomagnetism, Rock Magnetism and Palaeomagnetism, Marine Geosciences and Applied Geophysics, Appendix B: Trade-off between scalarmoment estimates and depths of CMTS, https://doi.org/10.1111/j.1365-246X.2011.05284.x, Earthquake interaction, forecasting, and prediction, Oceanic transform and fracture zone processes, Receive exclusive offers and updates from Oxford Academic, Copyright 2023 The Royal Astronomical Society. [3], Series of faults that offset the Pacific-Antarctic Ridge. They were generally too small to generate stable CMT results. The CMT methodology and format of the catalogue are described in Dziewonski (1981) and Ekstram (2005). 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. 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. Broader Terms: East Pacific Pacific Ocean South Pacific Southeast Pacific 3 and studied separately. Boettcher Is the singer Avant and R Kelly brothers? Tolstoy Bohnenstiehl et al. Hence, we cannot distinguish between those two models. W. Stewart Abstract. He attributed this to changes in the Euler pole for Pacific-Nasca plate motion during the last several million years. Kent D.V. Fox Sunrise: 06:37AM; Sunset: 05:22PM; Day length: 10h 45m; The local time in Stockholm County is currently the same as the solar time. The transform valley is 15-20 km wide and 2-4 km deep. The 30- to 42-km length that we used for the repeating events along the Heezen transform in Fig. Wolfe et al. Woodhouse 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. [] ( ) "eltanin fracture zone" in Chinese : "eltanin" in Chinese : "fracture zone" in Chinese : ; ; ; ; ; . 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 . G. It seems unlikely that our CMT location errors would change much over the length of the Tharp transform. Menke . Pacific Ocean Topography 70%. McGuire . 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? 4. The horizontal axis is parallel to computed transform directions; the vertical is perpendicular to it. Okal 'dextrally' (also known as right-laterally) which means if you If you are interested in visiting one of these Fracture Zone(s) in Undersea Features always contact the local Office of Natural Resources to gather all the regulations for fishing and outdoor adventures in the area. 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. 8) contains six events of Mw= 5.89 since 1971. The morphology of the Atlantis Fracture Zone is typical of that of slow-slipping transforms. . However, a major offset developed on this transform between 60 and 80 Ma, prior to the oldest dated rocks from the ridge. They represent a good laboratory for examining fault segments that slip aseismically, others that are well coupled, and the short recurrence times of earthquakes. [2] However, the total offset is about 1600km. Earthquakes of Mw 6.2-6.4 occur along each transform but larger events are confined to the eastern half of the Heezen, two parts of the Tharp and segments of the Hollister. 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. They may be regarded as quasi-periodic. It is that region where three of the four normal faulting earthquakes in Fig. Boettcher & McGuire (2009) conclude that the largest earthquakes on several fast-spreading transforms do not scale directly with the fault area shallower than their calculated 600 C isotherm. S. Carbotte kindly computed the bathymetric map in 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. Bathymetry from Ryan et al. The coefficient of variation (COV), the standard deviation, SD, divided by the average repeat time, is 0.26. Woodward Our calculations for all events have the advantage of having been corrected for lateral heterogeneity with the same model. The steep slope of about -2.9 for Mw > 6 is unusual. . This experiment addresses one component of the potential bias that may be present in CMT seismic moments. plates. Maternovskaya (2002) used nearby hydroacoustic stations to locate very small events and aftershocks along a number of oceanic transform faults. 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. Three normal-faulting events were found with T-axes nearly perpendicular to the Heezen transform (Fig. 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. Phipps Morgan 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. T.A. What are mid-ocean ridges? Dziewonski Excluding it does not change the average repeat time for events of Mw > 5.9; it increases the SD and COV slightly. florida a jurassic transform plate boundary. Of the 84 earthquakes from 1976 to 1989, we rejected seven CMT solutions. The 40Ar39Ar dating of rocks dredged . The Romanche Fracture Zone offsets the Mid-Atlantic ridge by 900 km (560 mi), making it the largest equatorial fracture zone in the Atlantic. If those short spreading centres are very young, they may not have had enough time to become oriented perpendicular to the transform. 5) and the 42-km section of the Heezen (Figs 4 and 7) are well isolated from other large shocks along those transforms we took the scatter in locations along them as a measure of L. Our knowledge of L is limited otherwise by the paucity of aftershocks of Mw > 5-5.5. 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. The three sets of large events have a repeat time of 13 yr and a COV of 0.13. "zone of fracture" in Chinese : , ; ; ,; ; "amsterdam fracture zone" in Chinese : "aseismic fracture zone" in Chinese : 2. The fault segment between -665 and -680 km (green symbols in Fig. How that may vary along strike and affect seismic coupling is unknown. 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. 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 Strike-slip faulting with moment magnitudes Mw up to 6.4 characterizes most of these events. 7, however, since it is located just to the east of other large shocks along the Heezen transform. A.M. SEANOE. 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. 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. From 1995-2003, Eltanin fracture zone was used with Antarctic Ocean and/or Pacific Ocean. Anderson FRACTURE ZONE. Our results indicate considerable variation in moment release and hence in fault coupling along the strike of the three Eltanin transforms. The normal-faulting event of 2001 August 6 is larger than that of any of the strike-slip events along the three Eltanin transforms.
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