The 2010 M w 7.2 El Mayor-Cucapah Earthquake Sequence, Baja California, Mexico and Southernmost California, USA: Active Seismotectonics along the Mexican Pacific Margin     

Egill Hauksson  Joann Stock  Kate Hutton  Wenzheng Yang  J. Antonio Vidal-Villegas  Hiroo Kanamori 《Pure and Applied Geophysics》2011,168(8-9):1255-1277

The El Mayor-Cucapah earthquake sequence started with a few foreshocks in March 2010, and a second sequence of 15 foreshocks of M?>?2 (up to M4.4) that occurred during the 24?h preceding the mainshock. The foreshocks occurred along a north?Csouth trend near the mainshock epicenter. The M _w 7.2 mainshock on April 4 exhibited complex faulting, possibly starting with a ~M6 normal faulting event, followed ~15?s later by the main event, which included simultaneous normal and right-lateral strike-slip faulting. The aftershock zone extends for 120?km from the south end of the Elsinore fault zone north of the US?CMexico border almost to the northern tip of the Gulf of California. The waveform-relocated aftershocks form two abutting clusters, each about 50?km long, as well as a 10?km north?Csouth aftershock zone just north of the epicenter of the mainshock. Even though the Baja California data are included, the magnitude of completeness and the hypocentral errors increase gradually with distance south of the international border. The spatial distribution of large aftershocks is asymmetric with five M5+ aftershocks located to the south of the mainshock, and only one M5.7 aftershock, but numerous smaller aftershocks to the north. Further, the northwest aftershock cluster exhibits complex faulting on both northwest and northeast planes. Thus, the aftershocks also express a complex pattern of stress release along strike. The overall rate of decay of the aftershocks is similar to the rate of decay of a generic California aftershock sequence. In addition, some triggered seismicity was recorded along the Elsinore and San Jacinto faults to the north, but significant northward migration of aftershocks has not occurred. The synthesis of the El Mayor-Cucapah sequence reveals transtensional regional tectonics, including the westward growth of the Mexicali Valley and the transfer of Pacific?CNorth America plate motion from the Gulf of California in the south into the southernmost San Andreas fault system to the north. We propose that the location of the 2010 El Mayor-Cucapah, as well as the 1992 Landers and 1999 Hector Mine earthquakes, may have been controlled by the bends in the plate boundary.  相似文献   

2009年萨摩亚—汤加特大地震触发的两次大震     

T.Lay  C.J.Ammon  H.Kanamori  L.Rivera  K.D.Koper  A.R.Hutko  李晶 《世界地震译丛》2011,(3)

特大地震(≥8.0级的地震)一般都含有构造板块之间边界岩体的突然滑动。这种板间的破裂通常出现在俯冲带特大逆冲事件的海沟斜坡区,会产生动态及静态应力变化,从而激活周边的板内余震(Christensen and Ruff,1988;Dmowskaetal,1988;Layetal,1989;Ammonetal,2008)。本文研究的地震序列展示一少见的例子———特大海沟斜坡的一次板内地震触发了广泛的板间断层活动,颠倒了典型的活动模式,从而广泛地扩大了地震和海啸灾害。2009年9月29日,在汤加俯冲带北端的外海沟斜坡发生矩震级8.1的正断层地震事件,该震开始破裂后的2分钟内,发生了总地震矩等于矩震级8.0级的第二个特大地震,它由两次(矩震级均为7.8级)板间下插逆冲大地震组成,导致了周边俯冲带巨型逆断层的破裂。联合的断层作用引发了海啸,局部地区抬升约12m,导致萨摩亚、美属萨摩亚和汤加192人死亡。地震信号的重叠掩盖了这样的事实:相隔约50km的性质不同的断层发生了不同几何形状的破裂,这些被触发的逆冲断层滑动只有通过详细的地震波分析才能揭示出来。在汤加北部俯冲带的大部分区域内,激活了广泛的板间和板内余震活动。  相似文献   

The Higo High-Grade Metamorphic Rocks in Japan as a Part of the Collisional Terrane Between the Sino-Korean and Yangtze Craton     

Yasuhito Osanai  Takuji Hamamoto  Hiroo Kagami  Kazuhiro Suzuki  Masaaki Owada  Atsushi Kamei   《Gondwana Research》1999,2(4):599-601

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Reply to comment by J. Trampert     

Jean-Paul Montagner  Phyllis Ho-Liu  Hiroo Kanamori 《Geophysical Journal International》1990,103(3):757-758

Books Reviewed in this Article:
Seismic tomography and mantle circulation Eds O'Nions, R. K. & Parsons, B., Royal Society of London Special Publication , 1989, ISBN 0854 033823.  相似文献   

Todorokite formation in seawater by microbial mediation     

Noburu Takematsu  Hiroo Kusakabe  Yoshio Sato  Shiro Okabe 《Journal of Oceanography》1988,44(5):235-243

Microbial manganese oxidation in seawater was carried out in enrichment cultures which were obtained from the seawater supply system at the Marine Science Museum, Tokai University (Shimizu-shi, Japan). The manganese oxide formed was well-crystallized todorokite. The major element composition was within the range of marine manganese concretions and the O/Mn molar ratio was 1.8. The conditions for formation of manganese oxide minerals in marine environments are discussed on the basis of these results.  相似文献   

Regional S-wave structure for southern California from the analysis of teleseismic Rayleigh waves     

David Hadley  Hiroo Kanamori 《Geophysical Journal International》1979,58(3):655-666

Summary. Teleseismic Rayleigh waves, M_S > 7.0, in the period range 14 to 28 s, are well recorded by the short-period Benioff array within southern California. Multiple arrivals that hinder the determination of local phase velocity curves are detected by narrow band-pass filtering. The records are then windowed on distinct, coherent peaks that move uniformly across the array. Four to seven stations are included in the determination of both the phase velocity across the array and the incidence azimuth. For earthquakes in the western Pacific, the derived incidence azimuths are systematically rotated counterclockwise by 2–16°. Most of this rotation results from refraction at the continental shelf. Phase velocity data for both the southern Mojave—central Transverse Ranges and the Peninsular Ranges are inverted to obtain regional 5-wave velocity models. The starting models are constructed from travel-time studies of local sources, both natural and artificial. Poisson's ratio as a function of depth is calculated for these two regions. The comparison of Poisson's ratio with laboratory ultrasonic studies requires a quartz-rich crust within the southern Mojave—central Transverse Ranges and a mafic crust within the Peninsular Ranges.  相似文献   

An estimation of the electric potential field generated by the diurnal atmospheric tide with the first negative mode excited in the lower ionosphere     

Hiroo Murata 《Planetary and Space Science》1974,22(4):569-582

The electric potential field in the ionosphere, which is generated by the atmospheric tide with the diurnal first negative mode excited in the lower ionosphere, is estimated. An equivalent mode is used instead of the exact mode in the following approximations : (i) the horizontal structure of the energy input is composed of the first two terms of the series expansion of the Hough function with the associated Legendre functions, and (ii) the Coriolis force is assumed to be constant in the equation of motion and the value appropriate to colatitude 45 being used. It is found that the equivalent mode gives a good approximation of the exact mode at midlatitudes in the neutral atmosphere. The result shows that the oscillation with its temperature variation of about 40 K in the excitation region generates the horizontal electric potential field of 10^?3 V/m in magnitude. The horizontal pattern of the field distribution is similar to that estimated by many authors. The maximum vertical electric current is about 3 × 10^?9 A/m² in the dynamo layer. It is found that the “virtual current,” introduced by Volland (1970) as a vertical current in and above the dynamo layer, in order to obtain a better agreement between theory and observations of the location of the diurnal symmetric Sq current vortex, is actually to be expected. The vertical current is very small, but this small steady current is necessary for the electric potential field of the dynamo layer to be mapped into the magnetosphere along the lines of the geomagnetic field.  相似文献   

Palaeomagnetism of stalagmites (speleothems) in SW Japan     

Hayao Morinaga  Hiroo Inokuchi  Katsumi Yaskawa 《Geophysical Journal International》1989,96(3):519-528

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Crustal structure and temporal velocity change in southern California   总被引：3，自引：0，他引：3  

Hiroo Kanamori  David Hadley 《Pure and Applied Geophysics》1975,113(1):257-280

Summary About twenty blasts are used to determine crustal structure and to monitor temporal seismic velocity changes in southern California. The shot time is determined up to 10 msec by using a disposable pick-up placed directly on the explosive. About 17 permanent stations and 20 temporary stations are used for the recordings. With a fast paper speed (typically 1 cm/sec) and the WWVB radio signals superposed on the seismic trace, absolute timing accuracy of up to 10 msec is achieved. A representative structure thus determined consists of a 4 km thick 5.5 km/sec layer underlain successively by 23.4 km thick 6.3 km/sec layer, 5.0 km thick 6.8 km/sec layer and 7.8 km/sec half space. The details of the lower crust are somewhat uncertain. This structure can explain the travel time data, corrected for the station and source elevations and for the station delays, to ±0.15 sec. Small but systematic temporal velocity changes up to 3% have been found for some of the profiles. If the effect of the migration of the shot point is small enough, these changes are larger than experimental errors and represent real temporal change in the material property between the shot point and the stations.Contribution No. 2530, Division of Geological Sciences, California Institute of Technology, Pasadena, California.  相似文献   

Long-period ground motion in the epicentral area of major earthquakes     

Hiroo Kanamori 《Tectonophysics》1974,21(4):341-356

In view of the potential importance of long-period ground motion in the design of large structures, near-field ground displacement is computed by the elastic dislocation theory for several earthquake fault models. The validity of such computations is confirmed by comparing the computed seismogram with the observed long-period seismogram of the 1923 Kanto earthquake. The ground motions are computed for three hypothetical earthquakes, a hypothetical Kanto earthquake, Tokai earthquake and Nemuro-Oki earthquake. The location and the nature of the faulting of these earthquakes are predicted by plate tectonics and precise earthquake mechanism studies. Major conclusions are: Tokyo may suffer, in the hypothetical Kanto earthquake, ground motions about half as large as those experienced in the 1923 Kanto earthquake; Hamamatsu, a large city on the Tokai coast, may experience in the hypothetical Tokai earthquake ground motions which are as large as, or even larger than, those experienced in the epicentral area of the 1923 Kanto earthquake; the hypothetical Nemuro-Oki earthquake may cause ground motions as large as those experienced in the 1968 Tokachi-Oki earthquake on the coastal cities in Hokkaido.  相似文献