Recent seismovolcanic crisis in northern Afar, Ethiopia
Recent seismovolcanic crisis in northern Afar, Ethiopia
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埃塞俄比亚阿法尔北部最近发生的地震火山危机
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发表时间：
2006
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影响因子：
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通讯作者：
A. Ayele
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作者：
G. Yirgu;A. Ababa;A. Ayele
2005年9月，埃塞俄比亚阿法尔中北部一个60公里长的裂谷段破裂。这次破裂发生在一段短暂但强烈的火山和构造活动期之后，在此期间发生了162次以上的地震(4级至5.2级)，并打开了一个400米长、80米宽的火山口(图L)。就其开放的空间范围和数量而言，这次事件是在陆地上观察到的最大的裂谷序列，可与沿大洋中脊长达10年的克拉夫拉(冰岛，1975-1984)事件相媲美。
阿法尔凹陷是一个三重裂谷交界处，红海和亚丁湾的扩张脊在陆地上出现，并与东非裂谷的北部延伸相接(图2a)。交界处位于地幔热柱上方或附近[例如，Courtillot等人，1984年；Montali等人，2004年]。凹陷的底部主要由过去300万年来的第四纪至第四纪侵位的玄武岩熔岩组成[例如，Kidane等人，2003年]。巨大而细长的玄武岩盾形火山醒目地矗立在玄武岩田野和沙地平原之上。阿法尔洼地是地球上最炎热和最干燥的地方之一，但那里的许多牧民通过从地热喷口(当地称为Boinas)蒸馏水来养活大量牧群。
A 60-kilometer-long rift segment ruptured in north central Afar, Ethiopia, in September 2005. This rupture followed a short but intensive period of volcanic and tectonic activity during which time more than 162 earthquakes (magnitudes 4.1—5.2) occurred and a 400-meter-long and 80-meter-wide volcanic vent opened (Figure l ). For its spatial extent and amount of opening, this event ranks as the largest observed rifting sequence to have occurred on land, comparable to the 10-yearlong Krafla (Iceland, 1975–1984) episode along a mid-ocean ridge.
The Afar depression is a triple rift junction where the Red Sea and Gulf of Aden spreading ridges emerge on land and meet the northern extension of the East African Rift (Figure 2a). The junction lies above or near a mantle plume [e.g., Courtillot et al., 1984; Montelli et al., 2004]. The floor of the depression is composed mostly of basalt lava emplaced during Plio-Quaternary times over the last three million years [e.g., Kidane et al., 2003]. Huge and elongate basaltic shield volcanoes conspicuously rise above basalt fields and sand plains. The Afar depression is one of the hottest and driest places on Earth, yet its many pastoralists support large herds by distilling water from geothermal vents (known locally as boinas).