Recent Rifting Events in the Southern Red Sea and Regional Implications

Abstract:

During the last decades, several rifting events on land have been observed along divergent plate boundaries, separating plates up to several meters in a few weeks. These events are typically accompanied by short-term seismic swarms (<15 days) and normal faulting, and are in some cases followed by eruptions as well. These on land rifting events represent, however, a very limited portion (< 2%) of global intrusions that take place in most cases along mid-ocean ridge systems. Here we focus on the southern Red Sea area, which is a part of the triple junction separating the Nubian, Somalian and Arabian plates where several earthquake swarms were recorded from 2000 to 2014. In three cases, these swarms were followed by eruptions within a year, at Jebel at Tair (2007) and in the Zubair Archipelago (40 km south) were two new volcanic islands developed in 2011 and 2013. Without the surface eruptions, these intrusive events may have remained unnoticed. Together the surface evidence of volcanic activity and recorded seismic swarms during the past two decades allow for a better definition of the overall magmatic activity in the southern Red Sea. We further discuss the possibility that Zubair, which is an emerged portion of a shallow 20 km-long by 5 km-wide NNW-SSE oriented platform, may be the surface expression of an active spreading center, comparable in size with other on land spreading centers. The recent concentration of activity at Zubair developed in a context of high regional magmatic and tectonic activity, including the rifting episode at Dabbahu (2005-2011), the rifting event in the Gulf of Aden (2010-2011) and the 2011 Nabro volcano eruption. Preliminary analysis of regional structural features and volcano lineaments suggest distinct intrusion paths and faulting running parallel to the three main active rift zone axes, and also along a dominant NE-SW oriented preexisting regional fault zones affecting the entire triple junction area.