Earthquakes are among the most devastating natural disasters on our planet. Especially large earthquakes with a magnitude above 7 are very dangerous. In order to understand the dynamics behind earthquakes, a look into the past is essential. However, this look does not go very far, as reliable seismological recordings only reach back about 100 years, and historical data are not sufficient in this respect. Researchers therefore rely on drilling cores from sediment deposits from the deep sea or even lakes to obtain precise data from prehistoric times. “The different sediment layers that are deposited year after year on the floor of our lakes and oceans provide long-term information on climatic and ecological conditions, but also record the disturbances induced by strong earthquake shaking that happened long ago, in the prehistoric past. Knowledge about these past events can help better understand earthquake occurrence and provide key information for assessing future earthquake hazard,” says Prof. Michael Strasser, head of the Sedimentary Geology working group at the Department of Geology and the Austrian Core Facility for scientific core analysis at the University of Innsbruck. “In light of this, the core from the Dead Sea, which my colleague Yin Lu is now analysing in Innsbruck, is a fantastic data set and very valuable for our research work.”
Dead Sea Archive
The Dead Sea Fault between the African and Arabian plates is one of the most famous earthquake-generating faults on earth. The Dead Sea is located approximately in the middle of this fault and, with 434 metres below sea level, is the lowest place on earth. Ten years ago, an international continental drilling program (ICDP) operation was carried out there to drill a core from the 300-metre-deep Dead Sea, which is 457 metres long and covers a period of 220,000 years in its sediments. “From the structures of the mud deposits, we can see when severe earthquakes took place and how strong these were ,” says Yin Lu.
Lu has been working at the Department of Geology since October 1, 2020, where he will be conducting research on different types of earthquake-related structures in this drilling core over the next few years as part of the Austrian Science Fund’s (FWF) Lise Meitner programme in the “DeadSeaQuakeRec” project, hosted by Ass. Professor Jasper Moernaut. Yin Lu has already worked intensively on this topic during his time at the Department of Geophysics at Tel Aviv University. First results were recently published in the journal Science Advances.
Strong earthquakes in short intervals
Together with international colleagues, Yin Lu identified more than 400 sedimentary deformations in the drilling core that indicate earthquake events. First results were recently published in the journal Science Advances. “Strong earthquakes are rare. However, since instrumental records do not go back very long, we know little about a possible cycle of strong earthquakes,” explains Lu. “In the sedimentary deposits from the Dead Sea, we can see a strikingly irregular recurrence of large earthquakes within the last 220,000 years, and this with a mean return time of of less than 1400 years. This rhythm is significantly shorter than previously considered and thus the seismic hazard in this region is underestimated. Up until now, research has assumed that strong earthquakes occur approximately every 11,000 to 7,000 years,” the geologist describes one of the main findings of the recent study. The work on this “fossil seismograph” will be continued intensively in the coming years. The researchers already have several plans for future research work during Yin Lu's stay: “For example, we will analyse this unique record with ultra-high resolution core scanners and also relate our findings to climatic developments that have led to drastic lake level changes at the Dead Sea, ” Jasper Moernaut adds.