The origin of tensile fracture lineaments     

Amos Nur 《Journal of Structural Geology》1982,4(1):31-40

Fracture-controlled lineaments, commonly seen where brittle basement is exposed at the earth's surface, are generally restricted to a small number of sets, with angles of 45–90° between sets. The length-frequency distribution of lineaments in each set follows a truncated Poisson function. Such lineaments usually show almost no shearing offset, suggesting a tensile origin. A simple mechanical model of tensile fracturing is used to explain the spacing, directions, and length of lineaments, as well as their depth-frequency distribution. Results suggest that the penetration depth of tensile fractures which produce lineaments at the earth's surface is directly related to their length and that the fracture density is inversely proportional to fracture depth. Finally, the angles between lineament sets may be controlled by the ratio of strength of unfractured rock to that of pre-existing fractures, which might heal with time. The most likely source of tension is tectonic uplift. Fractures due to typical uplifts of 0.5–1 km over distances of 10–100 km may penetrate as brittle fractures to several kilometres into the crust, perhaps to the depth at which seismic activity ceases.  相似文献   

Pore fluid pressure effects in anisotropic rocks: Mechanisms of induced seismicity and weak faults     

Qiang Chen  Amos Nur 《Pure and Applied Geophysics》1992,139(3-4):463-479

Many observations and studies indicate that pore fluid pressure in the crustal rocks plays an important role in deformation, faulting, and earthquake processes. Conventional models of pore pressure effects often assume isotropic porous rocks and yield the nondeviatoric pressure effects which seem insufficient to explain diverse phenomena related to pore pressure variation, such as fluid-extraction induced seismicity and crustal weak faults. We derive the anisotropic effective stress law especially for transversely-isotropic and orthotropic rocks, and propose that the deviatoric effects of pore fluid pressure in anisotropic rocks not only affect rock effective strength but also cause variation of shear stresses. Such shear stress variations induced by either pore pressure buildup or pore pressure decline may lead to faulting instability and trigger earthquakes, and provide mechanisms for the failure of crustal weak faults with low level of shear stresses. We believe that the deviatoric effects of pore fluid pressure in anisotropic rocks are of wide application in studies of earthquake precursors and aftershocks, oil and gas reservoir characterization, enhanced oil recovery, and hydraulic fracturing.  相似文献   

The genesis of the asphalt in the Dead Sea area     

Ora Amit  Amos Bein 《Journal of Geochemical Exploration》1979,11(3):211-225

The hydrocarbon occurrences of asphalts, heavy oils and oil shales in the Dead Sea area and the possible genetic relation between them have been studied. The similarity in organochemical characteristics, i.e., the elemental composition of asphaltenes, the distribution pattern of the saturated hydrocarbons and the predominance of V (over Ni)-porphyrins in both the oils and the asphalts indicate a close relation between them. On the other hand, dissimilarities in the same organochemical characteristics in both the asphalts and the oil shale exclude the hypotheses that asphalt was generated and expelled from the oil shales or that the shales were contaminated by oils. Water washing and biodegradation are considered to be the processes through which preferential depletion of hydrocarbons occurred, altering the oils to asphalts. The burial of the degraded asphalt to a relatively great depth resulted in a secondary generation of small amounts of light saturated hydrocarbons in these asphalts. The oils, which are thought to be the precursors of the asphalts, have either been flushed into the Dead Sea depression from the surrounding elevated areas or have seeped upwards from deep local accumulations in the graben.  相似文献   

Assessment of Hydraulic Parameters of the Aquifers Around the Sea of Galilee   总被引：1，自引：0，他引：1  

Gregory Bergelson  Ronit Nativ  Amos Bein 《Ground water》1998,36(3):409-417

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Fluid-pressure variations and fault creep in central California     

Ansel G. Johnson  Robert L. Kovach  Amos Nur 《Tectonophysics》1974,23(3):257-266

Observations of the change of water level in wells near the San Andreas fault in centra California indicate that there are pore-pressure changes associated with the process of fault creep. The sense of water-level and pore-pressure changes may indicate the direction of creep propagation.  相似文献   

Formation of mud ridge and runnels in the intertidal zone of the Severn Estuary,UK     

P.A. Carling  J.J. Williams  I.W. Croudace  C.L. Amos 《Continental Shelf Research》2009,29(16):1913-1926

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Zones of required investigation for earthquake-related hazards in Jerusalem   总被引：1，自引：1，他引：0  

Amos Salamon  Oded Katz  Onn Crouvi 《Natural Hazards》2010,53(2):375-406

Jerusalem was hit by earthquakes several times in its history, in the course of which none of the holy sites of the three main faiths of the western world escaped damage. Intensities of the last M_L 6.2, July 11, 1927 Dead Sea earthquake, reached MSK VIII in the Old City of Jerusalem and the surrounding villages. As future strong earthquakes are inevitable, the need for the evaluation of earthquake-related hazards is obvious. Only general geotechnical properties of the section exposed in the mountainous area of Jerusalem are available; therefore, the hazard assessment was conducted from a geological perspective. The hazards identified in this study are: (1) amplification of seismic acceleration due to soft rock and soil conditions; (2) amplification due to mountainous topography; (3) dynamic instability of natural slopes; and (4) potential failure of slopes that have undergone engineering development and were weakened due to damaging, steepening, overloading, and wetting beyond their natural state. We formulated relative grades of vulnerability for each of the hazards and delineated the zones that require further specific investigation. For practical use we constructed a summary map that combines the different hazard categories. Looking at the summary map, the ground at the central N–S axis zone across Jerusalem is the least vulnerable. The bedrock there is mostly hard carbonate, the topography is mild, and thus only the alluvial cover, if thicker than 3 m, should be considered sensitive. Yet although the natural hazard in this area is limited, the risk should not be underrated. Much of the city lies there, including buildings constructed before antiseismic codes were regulated, and traditional engineering practice should not be taken for granted as antiseismic proof either. Eastwards, the shear wave velocity (Vs) contrast between the hard and soft rocks as well as the notable topography in places, impose the potential for amplification. Slopes, either naturally or artificially cutting into the soft chalk, may expose the area to dynamic instability; thus, the ongoing extensive development of the city in this direction should certainly take into account all of this. West of the central axis, the potential of failure of both steep natural and urbanized slopes appears. Being a plausible direction for future urban expansion, these areas specifically call for careful environmental and engineering planning. For engineering purposes, however, a specific site investigation is still necessary. Nevertheless, the summary map established in this study sets up for Jerusalem, for the first time, a practical tool for environmental and municipal planning, emergency response planning, and civil protection.  相似文献   

Characterization of the hydrogeology of the sacred Gihon Spring, Jerusalem: a deteriorating urban karst spring   总被引：1，自引：0，他引：1  

Ronit Benami Amiel  Tamir Grodek  Amos Frumkin 《Hydrogeology Journal》2010,18(6):1465-1479

The Gihon Spring, Jerusalem, is important for the major monotheistic religions. Its hydrogeology and hydrochemistry is studied here in order to understand urbanization effects on karst groundwater resources, and promote better water management. High-resolution monitoring of the spring discharge, temperature and electrical conductivity, was performed, together with chemical and bacterial analysis. All these demonstrate a rapid response of the spring to rainfall events and human impact. A complex karst system is inferred, including conduit flow, fissure flow and diffuse flow. Electrical conductivity, Na⁺ and K⁺ values (2.0 mS/cm, 130 and 50 mg/l respectively) are very high compared to other nearby springs located at the town margins (0.6 mS/cm, 15 and <1 mg/l respectively), indicating considerable urban pollution in the Gihon area. The previously cited pulsating nature of the spring was not detected during the present high-resolution monitoring. This phenomenon may have ceased due to additional water sources from urban leakage and irrigation feeding the spring. The urbanization of the recharge catchment thus affects the spring water dramatically, both chemically and hydrologically. Appropriate measures should therefore be undertaken to protect the Gihon Spring and other karst aquifers threatened by rapid urbanization.  相似文献   

Unraveling rift margin evolution and escarpment development ages along the Dead Sea fault using cosmogenic burial ages     

A. Matmon  D. Fink  M. Davis  S. Niedermann  D. Rood  A. Frumkin 《Quaternary Research》2014

The Dead Sea fault (DSF) is one of the most active plate boundaries in the world. Understanding the Quaternary history and sediments of the DSF requires investigation into the Neogene development of this plate boundary. DSF lateral motion preceded significant extension and rift morphology by ~ 10 Ma. Sediments of the Sedom Formation, dated here between 5.0 ± 0.5 Ma and 6.2_− 2.1^+ inf Ma, yielded extremely low ¹⁰Be concentrations and ²⁶Al is absent. These reflect the antiquity of the sediments, deposited in the Sedom Lagoon, which evolved in a subdued landscape and was connected to the Mediterranean Sea. The base of the overlying Amora Formation, deposited in the terminal Amora Lake which developed under increasing relief that promoted escarpment incision, was dated at 3.3_− 0.8^+ 0.9 Ma. Burial ages of fluvial sediments within caves (3.4 ± 0.2 Ma and 3.6 ± 0.4 Ma) represent the timing of initial incision. Initial DSF topography coincides with the earliest Red Sea MORB's and the East Anatolian fault initiation. These suggest a change in the relative Arabian–African plate motion. This change introduced the rifting component to the DSF followed by a significant subsidence, margin uplift, and a reorganization of relief and drainage pattern in the region resulting in the topographic framework observed today.  相似文献   

Measuring earthquake risk concentration for hazard mitigation     

Richard Bernknopf  Paul Amos 《Natural Hazards》2014,74(3):2163-2192

One of the biggest impacts of a disaster is the effect it can have on community and regional housing and the ability of people, communities and regions to recover from the damages. Policy decisions involving investments in loss reduction measures and response and recovery are best informed by the integration of scientific and socioeconomic information. Natural scientists develop hazard scenarios for stakeholders and emergency officials to assess the impacts of a particular disaster outcome. Social scientists have found that housing losses and recovery affect individuals in lower socioeconomic status disproportionately. By combining socioeconomic status data from the US Census with an earthquake scenario for southern California, an event-driven conditional distribution of earthquake risk is used to prioritize investment decisions for earthquake hazard mitigation. Simulation of the damages in the scenario showed a statistically significant risk concentration in census tracts with large numbers of residents of lower socioeconomic status living in multi-family housing and mobile homes. An application of the approach is demonstrated in Los Angeles County as a decision criterion in a building retrofit program. The earthquake scenario was used to evaluate the economic benefits of a program for voluntary mitigation and a combined program of voluntary mitigation and regulated mitigation based on socioeconomic status (mandate requiring mitigation in census tracts meeting specific damage and income thresholds). Although the analysis is a hypothetical scenario based on a simulation of a great earthquake, the results and potential outcomes show that a regulated program with a socioeconomic decision criterion would have significant benefits to vulnerable populations.  相似文献