共查询到20条相似文献,搜索用时 15 毫秒
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Diane E. Moore David A. Lockner Hisao Ito Riuji Ikeda Hidemi Tanaka Kentaro Omura 《Pure and Applied Geophysics》2009,166(10-11):1669-1691
Samples of damage-zone granodiorite and fault core from two drillholes into the active, strike-slip Nojima fault zone display microstructures and alteration features that explain their measured present-day strengths and permeabilities and provide insight on the evolution of these properties in the fault zone. The least deformed damage-zone rocks contain two sets of nearly perpendicular (60–90° angles), roughly vertical fractures that are concentrated in quartz-rich areas, with one set typically dominating over the other. With increasing intensity of deformation, which corresponds generally to increasing proximity to the core, zones of heavily fragmented rock, termed microbreccia zones, develop between prominent fractures of both sets. Granodiorite adjoining intersecting microbreccia zones in the active fault strands has been repeatedly fractured and locally brecciated, accompanied by the generation of millimeter-scale voids that are partly filled with secondary minerals. Minor shear bands overprint some of the heavily deformed areas, and small-scale shear zones form from the pairing of closely spaced shear bands. Strength and permeability measurements were made on core collected from the fault within a year after a major (Kobe) earthquake. Measured strengths of the samples decrease regularly with increasing fracturing and fragmentation, such that the gouge of the fault core and completely brecciated samples from the damage zone are the weakest. Permeability increases with increasing disruption, generally reaching a peak in heavily fractured but still more or less cohesive rock at the scale of the laboratory samples. Complete loss of cohesion, as in the gouge or the interiors of large microbreccia zones, is accompanied by a reduction of permeability by 1-2 orders of magnitude below the peak values. The core samples show abundant evidence of hydrothermal alteration and mineral precipitation. Permeability is thus expected to decrease and strength to increase somewhat in active fault strands between earthquakes, as mineral deposits progressively seal fractures and fill pore spaces. 相似文献
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Aiming Lin Mikako Sano Maomao Wang Bing Yan Di Bian Ryoji Fueta Takashi Hosoya 《Journal of Seismology》2017,21(4):683-703
The Mw 6.2 (Mj 6.8) Nagano (Japan) earthquake of 22 November 2014 produced a 9.3-km long surface rupture zone with a thrust-dominated displacement of up to 1.5 m, which duplicated the pre-existing Kamishiro Fault along the Itoigawa–Shizuoka Tectonic Line (ISTL), the plate-boundary between the Eurasian and North American plates, northern Nagano Prefecture, central Japan. To characterize the activity of the seismogenic fault zone, we conducted a paleoseismic study of the Kamishiro Fault. Field investigations and trench excavations revealed that seven morphogenic paleohistorical earthquakes (E2–E8) prior to the 2014 Mw 6.2 Nagano earthquake (E1) have occurred on the Kamishiro Fault during the last ca. 6000 years. Three of these events (E2–E4) are well constrained and correspond to historical earthquakes occurring in the last ca. 1200 years. This suggests an average recurrence interval of ca. 300–400 years on the seismogenic fault of the 2014 Kamishiro earthquake in the past 1200 years. The most recent event prior to the 2014 earthquakes (E1) is E2 and the penultimate and antepenultimate faulting events are E3 and E4, respectively. The penultimate faulting event (E3) occurred during the period of AD 1800–1400 and is associated with the 1791 Mw 6.8 earthquake. The antepenultimate faulting event (E4) is inferred to have occurred during the period of ca. AD 1000–700, likely corresponding to the AD 841 Mw 6.5 earthquake. The oldest faulting event (E8) in the study area is thought to have occurred during the period of ca. 5600–6000 years. The throw rate during the early Holocene is estimated to be 1.2–3.3 mm/a (average, 2.2 mm/a) with an average amount of characteristic offset of 0.7–1.1 m produced by individual event. When compared with active intraplate faults on Honshu Island, Japan, these slip rates and recurrence interval estimated for morphogenic earthquakes on the Kamishiro Fault along the ISTL appear high and short, respectively. This indicates that present activity on this fault is closely related to seismic faulting along the plate boundary between the Eurasian and North American plates. 相似文献
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Studia Geophysica et Geodaetica - 相似文献
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Shi Lanbin 《中国地震研究》2004,18(3):281-299
Mantle xenoliths brought up by Cenozoic volcanic rocks onto the earth‘s surface may provide direct information about the upper mantle beneath the volcanic region. This paper presents the study on mantle xenoliths collected from Haoti village, Dangchang County, Gansu Province, western China. The main purpose of the study is to gain an insight into the thermal structure and rbeology of the upper mantle beneath the region. The results show that the upper mantle of the region is composed mainly of spinel lherzolite at shallower depth (52-75km), and garnet iberzolite at greater depth (greater than 75km), instead of harzburgite and dunite as proposed by some previous studies. The upper mantle geotherm derived from the equilibrium temperatures and pressures of xenoliths from the region is lower than that of North China, and is somewhat closer to the Oceanic geotherm. The crust-mantle boundary is determined from the geotherm to be at about 52km, and the Moho seems to be the transition zone of lower crust material with spinel iberzolite. If we take 1280℃ as the temperature of the top of asthenosphere, then the fithospbere-asthenosphere boundary should be at about 120km depth. The differential stress of the upper mantle is determined by using recrystallized grain size piezometry, while the strain rate and equivalent viscosity are determined by using the high temperature flow law of peridotite. The differential stress, strain rate and viscosity profiles constructed on the basis of the obtained values indicate that asthenospberic diapir occurred in this region during the Cenozoic time, resulting in the corresponding thinning of the lithosphere. However, the scale and intensity of the diapir was significantly less than that occurring in the North China region. Moreover, numerous small-scale shear zones with localized deformation might occur in the iithospberic mantle, as evidenced by the extensive occurrence of xenoliths with tabular equigranular texture. 相似文献
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Gradual Fault Weakening with Seismic Slip: Inferences from the Seismic Sequences of L’Aquila, 2009, and Northridge, 1994 总被引:1,自引:0,他引:1
Luca Malagnini Irene Munafo’ Massimo Cocco Stefan Nielsen Kevin Mayeda Enzo Boschi 《Pure and Applied Geophysics》2014,171(10):2709-2730
We estimate seismological fracture energies from two subsets of events selected from the seismic sequences of L’Aquila (2009), and Northridge (1994): 57 and 16 selected events, respectively, including the main shocks. Following Abercrombie and Rice (Geophys J Int 162: 406–424, 2005), we postulate that fracture energy (G) represents the post-failure integral of the dynamic weakening curve, which is described by the evolution of shear traction as a function of slip. Following a direct-wave approach, we compute mainshock-/aftershock-source spectral ratios, and analyze them using the approach proposed by Malagnini et al. (Pure Appl. Geophys., this issue, 2014) to infer corner frequencies and seismic moment. Our estimates of source parameters (including fracture energies) are based on best-fit grid-searches performed over empirical source spectral ratios. We quantify the source scaling of spectra from small and large earthquakes by using the MDAC formulation of Walter and Taylor (A revised Magnitude and Distance Amplitude Correction (MDAC2) procedure for regional seismic discriminants, 2001). The source parameters presented in this paper must be considered as point-source estimates representing averages calculated over specific ruptured portions of the fault area. In order to constrain the scaling of fracture energy with coseismic slip, we investigate two different slip-weakening functions to model the shear traction as a function of slip: (i) a power law, as suggested by Abercrombie and Rice (Geophys J Int 162: 406–424, 2005), and (ii) an exponential decay. Our results show that the exponential decay of stress on the fault allows a good fit between measured and predicted fracture energies, both for the main events and for their aftershocks, regardless of the significant differences in the energy budgets between the large (main) and small earthquakes (aftershocks). Using the power-law slip-weakening function would lead us to a very different situation: in our two investigated sequences, if the aftershock scaling is extrapolated to events with large slips, a power law (a la Abercrombie and Rice) would predict unrealistically large stress drops for large, main earthquakes. We conclude that the exponential stress evolution law has the advantage of avoiding unrealistic stress drops and unbounded fracture energies at large slip values, while still describing the abrupt shear-stress degradation observed in high-velocity laboratory experiments (e.g., Di Toro et al., Fault lubrication during earthquakes, Nature 2011). 相似文献
6.
Zhang Shimin 《中国地震研究》2006,20(2):202-215
INTRODUCTIONThe Yingjing-Mabian-Yanjinthrust fault zone lies on the southeastern margin of Tibet .It startsfromthe south of Tianquaninthe north,and it extends southwards through Yingjing, Emei , Ebian,Mabian,Lidian to the north of Yanjin of Yunnan, with a total length of 275 km. The fault zoneintersects withthe southernsegment of the Longmengshanthrust fault zone onits northernsegment andborders the Huayingshan-Lianfengfault zone onits southernsegment .It is a 30 km-wide NW-trendin… 相似文献
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Izvestiya, Physics of the Solid Earth - Abstract—In my comment on the paper by A.A. Lyubushin, G.N. Kopylova, and Yu.K. Serafimova, I focus on the problem of legitimacy of seismological data... 相似文献
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Brine migration and saltwater intrusion into freshwater aquifers are among the hazards which may result from injecting CO2 into deep saline formations. Comprehensive risk assessment should include estimates of the salinization of freshwater aquifers, preferably based on numerical simulation results. A crucial task is to choose an appropriate conceptual model and relevant scenarios. Overly conservative assumptions may lead to estimation of unacceptably high risks, and thus prevent the implementation of a CO2 storage project unnecessarily. On the other hand, risk assessment should not lead to an underestimation of hazards. This study compares two conceptual model approaches for the numerical simulation of brine-migration scenarios through a vertical fault and salt intrusion into a fresh water aquifer. The first approach calculates salt discharge into freshwater using an immiscible two-phase model with constant salinity in the brine phase. The second approach takes compositional effects into account and considers salinity as a variable parameter in the water phase. A spatial model coupling is introduced to adapt the increased model complexity to the required complexity of the physics. The immiscible two-phase model is applied in the CO2 storage reservoir and spatially coupled to a single-phase (water) two-component (water, salt) model, where salt mass fraction is a variable. A Dirichlet–Neumann technique is used for the coupling conditions at the interface of the two models. The results show that the predicted salt discharges can vary by orders of magnitude depending on the choice of the model. The implications of the results for risk assessment are discussed. 相似文献
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R.G. Ezquer M.A. Cabrera J. López M. Albornoz E. Garay 《Journal of Atmospheric and Solar》2010,72(2-3):206
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Spatial distributions of pressure and fluxes of precipitating magnetospheric plasma particles were constructed for the strong
magnetic storm of December 14 and 15, 2006. The calculations were performed using a model developed by E.A. Ponomarev. Geotail
and ACE satellite data were used to specify realistic initial and boundary conditions. The model results were compared with
the spatial distribution of the field of geomagnetic disturbances recorded by ground-based magnetic observatories during the
storm. The results show that the model (in its current form) provides good agreement between latitudinal displacements of
electron precipitations and auroral electrojets but fails to reflect their longitudinal structure. The model fails to yield
the strong westward electrojet observed by all auroral zone observatories during the main phase of the magnetic storm. 相似文献
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S. A. Fedotov A. V. Solomatin S. D. Chernyshev 《Journal of Volcanology and Seismology》2012,6(2):65-88
We consider the results from the ongoing 2010–2011 work on long-term earthquake prediction for the Kuril-Kamchatka arc based
on the pattern of seismic gaps and the seismic cycle. We develop a forecast for the next 5 years, from September 2011 to August
2016, for all segments of the Kuril-Kamchatka arc earthquake-generating zone. For 20 segments we predict the appropriate phases
of the seismic cycle, the normalized rate of small earthquakes (A10), the magnitudes of moderate earthquakes to be expected with probability 0.8, 0.5, and 0.15, and the maximum possible magnitudes
and probability of occurrence for great (M ≥ 7.7) earthquakes. This study serves as another confirmation that it is entirely
necessary to continue the work in seismic retrofitting in the area of Petropavlovsk-Kamchatskii. 相似文献
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The paper illustrates the opportunities provided by the use of data from Russian satellite experiments (CORONAS and Universitetsky-Tatiana of Meteor series) on the measurement of fluxes and spectra of solar cosmic rays at altitudes of 370–1000 km for simulation of the ozonosphere state. The results of photochemical simulation and observational data analysis showing the influence of solar protons on polar ozonosphere and lower ionosphere in periods of solar proton events (SPE) on November 4, 2001, October 28, 2003, and January 16, 2005 are presented. It is shown that the solar proton action causes ozone depletion in the mesosphere above the polar regions. The strongest depletion (up to 70%) was caused by the SPE that occurred on October 28, 2003. 相似文献
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V. N. Dvigalo I. V. Melekestsev A. V. Shevchenko I. Yu. Svirid 《Journal of Volcanology and Seismology》2013,7(6):345-361
This paper presents the results from the detailed analysis of aerial photographs and space images for the Kizimen area, which characterize the geologic and geomorphologic effects of the ongoing eruption over the 2010–2011 period. It is shown that the total volume (>0.5 km3) and total mass (>109 t) of the discharged (resurgent plus juvenile) material makes this eruption the most productive in Kamchatka for the first 12 years of the 21st century. The dominant component (>90%) is juvenile material with andesitic composition. The pyroclastics (tephra, deposits of the juvenile pyroclastic avalanches and incandescent debris avalanches) comprise >0.3 km3and >0.45× 109 t, the lava (a very thick block lava flow 3.052 km long and 2.163 km2 in area) occupies about 0.195 km3 and 0.45 × 109 t. With the exception of the tephra, which fell over an area of about 100000 km2, the rest of the material was accumulated on the Kizimen cone and at its base. The mean discharge rate of juvenile ejecta was about 15 m3/s (29 t/s) for 13 months (November 11, 2010 to December 11, 2011). Appreciable changes also occurred at the near-summit part of the volcano’s cone. 相似文献
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K. G. Ivanov 《Geomagnetism and Aeronomy》2010,50(3):285-297
The dynamics of the large-scale open field and solar activity at the second stage of the MHD process, including the origination
and disappearance of the four-sector structure during the decline phase of cycle 23 (the stage when the blocking field is
displaced from the main zone of active longitudes), has been considered. Extremely fast changes in the scales of one of new
sectors (from an extremely small sector (“singularity”) to a usual sector that originated after the uniform expansion (“explosion”)
of singularity with a “kick” into the zone of active longitudes, westward motion of the MHD disturbance front in the direction
of solar rotation, and formation of an active quasi-rigidly corotating sector boundary responsible for the heliospheric storm
of November 2004) have been detected in the field dynamics. It has been indicated that a very powerful group of sunspots AR
10656 (which disappeared after the explosion) with an area of up to 1540 ppmh (part per million hemisphere), a considerable
deficit of the external energy release, and zero geoeffectiveness in spite of the closeness to the Earth helioprojection existed
within singularity. It has been assumed that the energy escaped from this group with effort owing to the interaction between
coronal ejections and narrow sector walls (singularity), and a considerable part of the energy was released in the outer layers
of the convective zone, as a result of which singularity exploded and this explosion was accompanied by the above effects
in the large-scale field and solar activity. 相似文献
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