El Khrepy Sami, Koulakov Ivan, Gerya Taras, Al-Arifi Nassir, Alajmi Mamdouh S, Qadrouh Ayman N
Natural hazards and mineral resources chair, Geology and Geophysics Department, King Saud University, P.O. Box 2455, Riyadh, 11451, Saudi Arabia.
Seismology Department, National Research Institute of Astronomy and Geophysics (NRIAG), Helwan, 11421, Egypt.
Sci Rep. 2021 Mar 10;11(1):5594. doi: 10.1038/s41598-021-84952-w.
Lithosphere extension, which plays an essential role in plate tectonics, occurs both in continents (as rift systems) and oceans (spreading along mid-oceanic ridges). The northern Red Sea area is a unique natural geodynamic laboratory, where the ongoing transition from continental rifting to oceanic spreading can be observed. Here, we analyze travel time data from a merged catalogue provided by the Egyptian and Saudi Arabian seismic networks to build a three-dimensional model of seismic velocities in the crust and uppermost mantle beneath the northern Red Sea and surroundings. The derived structures clearly reveal a high-velocity anomaly coinciding with the Red Sea basin and a narrow low-velocity anomaly centered along the rift axis. We interpret these structures as a transition of lithospheric extension from continental rifting to oceanic spreading. The transitional lithosphere is manifested by a dominantly positive seismic anomaly indicating the presence of a 50-70-km-thick and 200-300-km-wide cold lithosphere. Along the forming oceanic ridge axis, an elongated low-velocity anomaly marks a narrow localized nascent spreading zone that disrupts the transitional lithosphere. Along the eastern margins of the Red Sea, several low-velocity anomalies may represent crustal zone of massive Cenozoic basaltic magmatism.
岩石圈伸展在板块构造中起着至关重要的作用，它既发生在大陆（如裂谷系统），也发生在海洋（沿大洋中脊扩张）。红海北部地区是一个独特的天然地球动力学实验室，在这里可以观察到正在进行的从大陆裂谷作用向大洋扩张的转变。在此，我们分析了埃及和沙特阿拉伯地震台网提供的合并目录中的走时数据，以构建红海北部及其周边地壳和上地幔顶部的三维地震速度模型。推导得出的结构清楚地揭示了一个与红海盆地重合的高速异常以及一个沿裂谷轴中心的狭窄低速异常。我们将这些结构解释为岩石圈伸展从大陆裂谷作用向大洋扩张的转变。过渡性岩石圈表现为一个主要为正的地震异常，表明存在一个厚度为50 - 70公里、宽度为200 - 300公里的冷岩石圈。沿着正在形成的大洋中脊轴，一个细长的低速异常标志着一个狭窄的局部新生扩张带，它破坏了过渡性岩石圈。沿着红海的东部边缘，几个低速异常可能代表了新生代大规模玄武岩浆作用的地壳区域。
