Spätquartäre Erdbebengeschiche von Festgesteins-Abschiebungen ermittelt durch 36Cl, LiDAR und REE Messungen, sowie Schlussfolgerungen zur methodischen Anwendung, zu den Bewegungsraten der Störungen und zum seismischen Zyklus

• Antragstellerin: Dr. Silke Mechernich
• Fachliche Zuordnung: Paläontologie
• Förderung: Förderung von 2013 bis 2021
• Projektkennung: Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 234274331

This study aims to investigate the Late Quaternary seismic activity of bedrock normal faults on Crete (Greece). On Crete two perpendicular sets of active normal faults prevail: one strikes parallel the Hellenic trench in E-W direction, while a second one results in arc-perpendicular extension. The surface rupture length of single fault segments ranges between 5 and 20 km and locally these faults are organized in larger and more complex fault zones. Typically the faults expose well-preserved limestone fault scarps with a height of 6-30 m, resulting from a stepwise exhumation during cumulative displacements by strong earthquakes. In this study the age of five fault scarps will be determined using 36Cl exposure dating, which allows the long-term slip rate of the normal faults to be revealed. Age and magnitude of individual earthquakes can be determined by continuous 36Cl measurements; however, this requires a tedious and expensive procedure. Recently, rare earth element (REE) concentrations on limestone fault scarps revealed characteristic REE patterns due to different horizons of soil interaction that are presumably caused by stepwise, earthquake-related exhumation of the fault scarp. Furthermore, bands of different weathering on the fault scarps, indicated by measurements of light detection and ranging (LiDAR), infer different steps of exhumation as well. The innovative idea of this study is to determine the exact location of different exhumation stages using both REE and LiDAR measurements followed by selected analysis of 36Cl to date the earthquake events. This procedure is expected to significantly reduce the amount of required 36Cl samples while simultaneously improving the accuracy of the reconstructed earthquake history.The obtained data will reveal the complete history of strong earthquakes on the investigated faults since they will include their date, magnitude and recurrence interval. A comparison of the earthquake history on adjacent faults can reveal several aspects of fault behavior on Crete, e.g. if more than one fault segment ruptures during a single earthquake, or if earthquakes are triggered by a stress change induced from a previous earthquake. Such interactions between different faults will be additionally evaluated using Coulomb failure stress modeling. In the case that several fault segments ruptured during one earthquake, the currently assumed maximum capable magnitude of Mw 6.8 would be underestimated. In addition, the time passed since the last earthquake on each fault reveals its seismic loading and thus the capability of generating a strong earthquake in the near future. All in all, the investigations are expected to reveal major aspects of the fault mechanics and will help understanding the dynamic properties of similar geologic settings.

• DFG-Verfahren: Sachbeihilfen