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71.
Cheaib Aya Lacroix Pascal Zerathe Swann Jongmans Denis Ajorlou Najmeh Doin Marie-Pierre Hollingsworth James Abdallah Chadi 《Landslides》2022,19(3):603-619
Landslides are the main secondary effects of earthquakes in mountainous areas. The spatial distribution of these landslides is controlled by the local seismic ground motion and the local slope stability. While gravitational instabilities in arid and semi-arid environments are understudied, we document the landslides triggered by the Sarpol Zahab earthquake (November 12, 2017, Mw7.3, Iran/Iraq border), the largest event ever recorded in the semi-arid Zagros Mountains. An original earthquake-induced landslide inventory was derived, encompassing landslides of various sizes and velocities (from rapid disrupted rockfalls to slow-moving coherent landslides). This inventory confirms the low level of triggered landslides in semi-arid environments. It also displays clear differences in the spatial and volumetric distributions of earthquake-induced landslides, having 386 rockfalls of limited size triggered around the epicenter, and 9 giant (areas of ca. 106 m2) active and ancient deep-seated landslides coseismically accelerated at locations up to 180 km from the epicenter. This unusual distant triggering is discussed and interpreted as an interaction between the earthquake source properties and the local geological conditions, emphasizing the key role of seismic ground motion variability at short spatial scales in triggering landslides. Finally, the study documents the kinematics of slow-moving ancient landslides accelerated by earthquakes, and opens up new perspectives for studying landslide triggering over short (~?1–10 years) and long-time (~?1000–10,000 years) periods.
相似文献72.
Mikbi intrusion(MI) is a part of the Neoproterozoic Nubian Shield located along the NE-SW trending major fracture zones prevailing southern Eastern Desert of Egypt. In this study, we present for the first time detailed mineralogical and bulk-rock geochemical data to infer some constraints on the parental magma genesis and to understand the tectonic processes contributed to MI formation. Lithologically, it is composed of fresh peridotite, clinopyroxenite, hornblendite, anorthosite, gabbronorite, pyroxene amphibole gabbro, amphibole gabbro and diorite. All rocks have low Th/La ratios(mostly <0.2) and lack positive Zr and Th anomalies excluding significant crustal contamination. They show very low concentrations of Nb, Ta, Zr and Hf together with sub-chondritic ratios of Nb/Ta(2-15) and Zr/Hf(19-35),suggesting that their mantle source was depleted by earlier melting extraction event. The oxygen fugacity(logfO_2) estimated from diorite biotite is around the nickel-nickel oxide buffer(NNO) indicating crystallization from a relatively oxidized magma. Amphiboles in the studied mafic-ultramafic rocks indicate relative oxygen fugacity(i.e. ΔNNO; nickel-nickel oxide) of 0.28-3 and were in equilibrium mostly with 3.77-8.24 wt.% H_2 Omelt(i.e. water content in the melt), consistent with the typical values of subduction-related magmas. Moreover, pressure estimates(0.53-6.79 kbar) indicate polybaric crystallization and suggest that the magma chamber(s) was located at relatively shallow crustal levels. The enrichment in LILE(e.g., Cs, Ba, K and Sr) and the depletion in HFSE(e.g., Th and Nb) relative to primitive mantle are consistent with island arc signature. The olivine, pyroxene and amphibole compositions also reflect arc affinity. These inferences suggest that their primary magma was derived from partial melting of a mantle source that formerly metasomatized in a subduction zone setting. Clinopyroxene and bulkrock data are consistent with orogenic tholeiitic affinity. Consequently, the mineral and bulk-rock chemistry strongly indicate crystallization from hydrous tholeiitic magma. Moreover, their trace element patterns are subparallel indicating that the various rock types possibly result from differentiation of the same primary magma. These petrological, mineralogical and geochemical characteristics show that the MI is a typical Alaskan-type complex. 相似文献
73.
Identification of sinkhole development mechanism based on a combined geophysical study in Nahal Hever South area (Dead Sea coast of Israel) 总被引：2，自引：0，他引：2
Michael Ezersky Anatoly Legchenko Christian Camerlynck Abdallah Al-Zoubi 《Environmental Geology》2009,58(5):1123-1141
Seismic refraction, magnetic resonance sounding (MRS), and the transient electromagnetic (TEM) method were applied to investigate
the geological and hydrogeological conditions in the Nahal Hever South sinkhole development area at the Dead Sea (DS) coast
of Israel. Microgravity and MRS results reliably reveal large karst cavity in the central part of investigated area. The map
of the seismic velocity shows that sinkholes in Nahal Hever can be divided into two major groups: sinkholes close to the salt
edge and sinkholes over compact salt formations between a few tens to a hundred meters from the major cavern. The present
study shows that the formation of sinkholes of the first group is caused by soil collapsing into the cavern. In the area occupied
by sinkholes of the second group, karst was not detected either by MRS or by seismic diffraction methods. TEM results reveal
shallow clay layer saturated with DS brine underlain sinkholes of this group. It allows suggestion that the water drainage
and intensive water circulation during rain events wash out fine rock particles from the unsaturated zone into the pre-existing
cavern, initiating the formation of sinkholes of the second group. Karst development takes place at a very low bulk resistivity
(<1 Ω m) of the DS aquifer, attesting to the fact that pores are filled with a highly saline solution. Refilling of the karstic
cavities with collapsing and flushed soil slows down sinkhole development in the area. The sinkhole formation cycle at the
site is estimated at 10 years. Sinkhole development throughout the studied area is triggered by a drop in the level of the
DS, which reduces the head of the confined aquifer and the strength of the overlain sediments.
相似文献
| Abdallah Al-ZoubiEmail: |
74.
Mohamed Abdallah Gad DARWISH 《《地质学报》英文版》2011,85(4):881-898
A suite of elements(Ag,Au,Ba,Bi,Cd,Co,Cr,Cu,Ga,Hf,Hg,Mn,Mo,Ni,Pb,Rb,Sb,Se, Sr,Te and Zn),total organic carbon(TOC)and pH were analyzed in stream sediment and tailing samples from Um Shashoba area,in order to evaluate Au placer and the sediments being impacted by old mining activities.Analytical results were examined using statistical,graphical and mapping methods.In spite of the results revealing that Au and most of the elements in sediments were in general significantly lower than those in tailing,Au wa... 相似文献
75.
Flash flood risk estimation along the St. Katherine road,southern Sinai,Egypt using GIS based morphometry and satellite imagery 总被引：7，自引：4，他引：3
Ahmed M. Youssef Biswajeet Pradhan Abdallah Mohamed Hassan 《Environmental Earth Sciences》2011,62(3):611-623
Flash floods are considered to be one of the worst weather-related natural disasters. They are dangerous because they are
sudden and are highly unpredictable following brief spells of heavy rain. Several qualitative methods exist in the literature
for the estimations of the risk level of flash flood hazard within a watershed. This paper presents the utilization of remote
sensing data such as enhanced Thematic Mapper Plus (ETM+), Shuttle Radar Topography Mission (SRTM), coupled with geological,
geomorphological, and field data in a GIS environment for the estimation of the flash flood risk along the Feiran–Katherine
road, southern Sinai, Egypt. This road is a vital corridor for the tourists visiting here for religious purposes (St. Katherine
monastery) and is subjected to frequent flash floods, causing heavy damage to man-made features. In this paper, morphometric
analyses have been used to estimate the flash flood risk levels of sub-watersheds within the Wadi Feiran basin. First, drainage
characteristics are captured by a set of parameters relevant to the flash flood risk. Further, comparison between the effectiveness
of the sub-basins has been performed in order to understand the active ones. A detailed geomorphological map for the most
hazardous sub-basins is presented. In addition, a map identifying sensitive sections is constructed for the Feiran–Katherine
road. Finally, the most influenced factors for both flash flood hazard and critical sensitive zones have been discussed. The
results of this study can initiate appropriate measures to mitigate the probable hazards in the area. 相似文献
76.
里散半岛位于非洲板块和阿拉伯板块支接处的死海盆地中。该盆地面积大，构造简单且有下沉运动，说明它是一位张型盆地。由重力异常数据发现死海盆地可划分成沿南北延伸各约３０ｋｍ长的几个块体，里散半岛是其一最深的一个。一生代沉积厚度约６ｋｍ，更新世沉积厚度为９ｋｍ。死海盆地的拉张距离为２０ｋｍ，表明死海盆地的年龄约３．３Ｍａ。里散半岛下部的前寒武纪结晶基底磁化率较高，这与区内延续的构造活动性有关。 相似文献
77.
This paper presents a historical account of Brazilian public policy on fisheries subsidies, and a discussion of problems and limitations resulting from such policy. From the 1960s to the mid-1980s, public policies led to a great increase in fisheries catch without appropriate consideration for the long-term sustainability of the resources, resulting in declining catches over the years. The goals of current Brazilian public policy on fisheries will not help in reducing overexploitation. This is because these policies are too optimistic about the abundance of fish in Brazil's EEZ, and are not accompanied by a fisheries management plan that is likely to work. 相似文献
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