Heat flow anomalies in the Gulf of Cadiz and off Cape San Vincente, Portugal
Heat flow anomalies in the Gulf of Cadiz and off Cape San Vincente, Portugal
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葡萄牙加的斯湾和圣文森特角附近的热流异常
DOI：
10.1016/j.marpetgeo.2008.08.006
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发表时间：
2009
影响因子：
4.2
通讯作者：
A. Kopf
中科院分区：
文献类型：
--
作者：
I. Grevemeyer;N. Kaul;A. Kopf
大地热流异常是构造活动环境的重要信息。加迪斯湾和邻近地区受到非洲和欧洲板块会聚的影响，造成广泛的变形和断层。活动性逆冲断层引起热量的横向运动和平流，从而产生地表热流的系统变化。2003年12月，研究船索内号在加迪斯湾进行SO 175号巡航时，在最近重点研究活动的两个地点收集了新的热流数据：㈠加迪斯湾沉积棱柱和㈡ Marques de Pombal悬崖。这两个特征也被认为是1755年里斯本大地震和海啸的潜在震源区。马蹄形深海平原东端的背景热流约为52- 59 mW/m ~ 2。在加迪斯棱镜湾上空，向东约120公里处，热流从157 mW/m2下降到45 mW/m2的异常低值。这种低值和热流趋势是典型的活动逆冲推覆，支持东倾逆冲断层的想法。滑动速率为每年10± 5毫米，假设断层倾角为2°。然而，倾角为5°的断层将导致每年1.5- 5毫米的滑动速率，这表明俯冲作用基本上已经停止。根据地震数据，Marques de Pombal断层被解释为位于圣文森特角向西约100公里处的活动断层系统的一部分。断层上的热流受1 km高的陡崖引起的热折射的影响。热模型表明，沿断层的滑动率沿着必须是小的或剪切应力作用在断层上是相当高的。然而，相对于其他断层带，可以合理地假设断层的滑动速率很小。
Heat flow anomalies provide critical information in active tectonic environments. The Gulf of Cadiz and adjacent areas are affected by the plate convergence between Africa and Europe, causing widespread deformation and faulting. Active thrust faults cause lateral movement and advection of heat that produces systematic variations in surface heat flow. In December 2003 new heat flow data were collected during the research vessel Sonne cruise SO175 in the Gulf of Cadiz over two sites of recent focused research activity: (i) the Gulf of Cadiz sedimentary prism and (ii) the Marques de Pombal escarpment. Both features have also been discussed as potential source areas of the Great Lisbon earthquake and tsunami of 1755. Background heat flow at the eastern terminus of the Horseshoe abyssal plain is about 52–59mW/m2. Over the Gulf of Cadiz prism, heat flow decreases from ∼57mW/m2to unusually low values of 45mW/m2roughly 120km eastward. Such low values and the heat flow trend are typical for active thrusting, supporting the idea of an east-dipping thrust fault. Slip rates are 10±5mm per year, assuming that the fault dips at 2°. A fault dipping at 5°, however, would result into slip rates of 1.5–5mm per year, suggesting that subduction has largely ceased. Based on seismic data, the Marques de Pombal fault is interpreted as part of an active fault system located ∼100km westward of Cape San Vincente. Heat flow over the fault is affected by refraction of heat caused by the 1km high escarpment. Thermal models suggest that the slip rate along the fault must either be small or shear stresses acting on the fault are rather high. With respect to other fault zones, however, it is reasonable to assume that the fault's slip rate is small.