ALASKA: Morphologie als dynamischer Ausdruck von Änderungen der internen Struktur der Oberplatte: Tiefenseismische und bathymetrische Studien der Subduktionszone vor Alaska und ein globaler Vergleich

• Antragstellerin: Dr. Anne Krabbenhöft
• Subject Area: Physik des Erdkörpers
• Term: from 2013 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 236456676

The seismogenic zone is that part of a subduction zone where the largest earthquakes worldwide nucleate. Recent studies show that 1.) the landward termination of the seismogenic zone at depth coincides with the shelf break at the seafloor and 2.) large faults (so called splay faults) connect the seaward part of the seismogenic zone with the seafloor. The activation of such splay faults during a subduction earthquake might act as extension of the subduction fault, thus enlarging the seismic energy released during the earthquake. Additionally, splay faults, reaching the seafloor, enhance the potential of generating a large tsunami in connection with the subduction earthquake, raising the hazard potential for the coastal regions.Many open questions arise, when dealing with subduction related great earthquakes. Some of them relate to the lateral variability of subduction zones: How do lateral variations of the upper and lower plates along continental margins affect the location and recurrence of great subduction earthquakes? Do subducting bathymetric features, like seamounts, act as nucleation areas which favor earthquake generation or do they rather form barriers for great subduction earthquakes?One contribution to address these open questions is to analyze two unpublished wide-angle seismic profiles off Kodiak Island, Alaska, in combination with the re-processing and re-interpretation of multichannel seismic data. Additionally, bathymetric data of the Alaska margin would provide the link between subsurface structures derived from the interpretation of the seismic data and the seafloor morphology. The proposed datasets are of high quality and meet todays standards.The results concerning the morphological structure in relation with the internal structure of the Alaska subduction zone will be put in a global context. I will compare the accretionary Alaska subduction zone with seismic and bathymetric data of other subduction settings worldwide (e.g. the erosive Java, accretionary Sumatra, South- and Middle-American margins). This might give new insight on the influence of different input into subduction settings (e.g. the sedimentary input, morphology of the incoming plate, like seamounts). Similarities as well as differences between accretionary and erosive subduction zones with the potential to create great (MW > 8) earthquakes might answer some of the above listed open questions, especially regarding the location and length of the seismogenic zone. Die seismogene Zone ist der Bereich der Plattengrenze an Subduktionszonen, in dem die größten Erdbeben weltweit erzeugt werden. Neueste Untersuchungen zeigen 1.) dass bei Subduktionszonen die Lage der seismogenen Zone in der Tiefe mit der Schelfkante am Meeresboden zusammenfällt, und 2.) Verbindungen der Subduktionsverwerfung mit dem Meeresboden durch Störungen am unteren Kontinentalhang, sog. splay faults. Die Aktivierung dieser Störzonen durch ein großes Subduktionsbeben kann die Verlängerung der seismogenen Zone erwirken. Die Verlängerung der Bruchzone bis zum Meeresboden stellt zusätzlich eine Erhöhung des Gefahrenpotentials zur Erzeugung von Tsunamis während großer Erdbeben dar.

• DFG Programme: Sachbeihilfen