Submarine Hazards at Continental Margins

Submarine Geohazards

Earthquakes, volcanic eruptions, coastal and submarine landslides and their consequences like tsunamis are natural phenomena and represent hazards to near-shore and offshore life and infrastructure. They can cause severe damage to areas on local or regional scales and hundreds of thousands of casualties.

Despite intense investigation, earthquakes remain insufficiently understood. Their precise forecast and their tsunami potential are very difficult to predict. Earthquakes and other processes can cause slope instability and subsequent failure of sediments and/or rocks. The rapid displacement of large masses and the associated changes in seafloor topography can destroy offshore infrastructure and trigger large-scale tsunamis.

Scientists involved in this project have focused their activities on the following two themes:

Assessment of the link between the structure and dynamics of subduction zones and the megaearthquake cycle,
Slope stability issues at continental margins.

The main emphasis of the newly established Junior Research Group (JRG) is the analysis of submarine slope failures and associated hazards. We have investigated numerous slides in different tectonic settings including active and passive margins, as well as lakes by means of hydroacoustic, seismic, and sedimentological/geotechnical methods.

Submarine landslides: a global phenomenon

Submarine landslides occur on continental margins worldwide. The largest known slides, however, occur on passive margins, e.g. the Storegga slide off Norway and giant slides off NW-Africa. Slides might reach volumes of more than 20.000 km³, affect areas of more than 90.000 km² and show run-out distances of up to 800 km. Active margins are characterized by more frequent but generally smaller events.

Submarine mass wasting plays an important role during the evolution of continental margins. The main research focus, however, is related to the hazards associated with submarine sliding. Submarine slides are able to destroy offshore infrastructure (e.g., cables, pipelines, and platforms) and generate tsunamis. It is also discussed whether submarine slides can release large amounts of greenhouse gases bound in hydrates by the removal and liquefaction of the involved sediment.

Today, the importance of submarine slope failure processes rises with increasing infrastructure on the sea-floor and near the coasts. A variety of socio-economical branches, including energy, communication, navigation, tourism, fisheries, military and science extend their interest further offshore and deeper into the sea. In the view of a warming future ocean with rising sea-level and intensified human activities, the increasing significance of slope stability issues is evident.The investigation of different types of slides provides the chance to gain a better understanding of the causes and consequences of submarine slope failures. In this context, a variety of submarine slope failures from different geological settings are chosen and analyzed by geophysical, sedimentological and geotechnical methods. Dating of slides is critical in order to evaluate the relationship between mass wasting and environmental conditions.

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