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Japan is known for beautiful cherry trees and for disastrous earthquakes. During the cherry blossom season in April 2016, Kyushu (the southwestern main island of Japan) was hit by a magnitude 7 earthquake at 1:25 AM local time. The earthquake struck the densely populated area of Kumamoto city and forty lives perished during the event. The earthquake caused hundreds of landslides and widespread damage to local infrastructure and buildings, among those the famous Kumamoto castle. Total cost of the damage is estimated at several billion dollars.
Understanding the response of the Earth's surface to the earthquake is critical when designing for earthquake resistant structures. This involves the analysis of seismic waves, which is required to understand the rupture process of an earthquake deep within the Earth's crust. The project "I3 - Towards non-ergodic time-dependent ground motion models" focuses on the evolution of subsequent aftershocks of the magnitude 7 main shock. The physical properties of the fault and the surrounding ground were severely altered and we investigate how this change affects aftershocks and their impact on strong ground motion at the surface. In connection with project "P1 - Landslide Prediction under Changing Boundary Conditions" we investigate the landslides triggered by the earthquake. The collaboration between geomorphologists and seismologists in this task force group allows the development of a multidisciplinary model for explaining the location and size of earthquake-triggered landslides.
The picture (jishin no sakura) - Cherry Blossoms of an Earthquake - shows at each seismic station of Kyushu the horizontal particle acceleration, i.e. in which direction and by how much the ground moved when seismic waves arrived at the station. And just like each blossom of a cherry tree is unique in its appearance, so is earthquake motion unique at each site. The representation of the particle acceleration here is inspired by the cherry blossom. The size and color of the blossoms relate to the amplitude of the ground motion and each petal is one measurement per time.
In the wake of changing hydro-climatological, geo-physical and socio-economic conditions the magnitude, frequency and impact of certain types of natural hazards are likely bound to change as well. This is highly of utmost importance for many regions in the world where risks due to natural hazards have to be managed and mitigated and this is where the research training group “Natural hazards and risks in a changing world (NatRiskChange)” aims to foster the scientific knowledge basis. This research training group started on October 1st 2015 and is funded by the Deutsche Forschungsgemeinschaft DFG. The central goal of NatRiskChange is to pursue the development of methods to improve hazard and risk analysis and quantification based on the transient, non-stationary nature of hazards and risks in response to changing natural and anthropogenically altered components of the Earth system. Key scientific aims are the development, testing, and pilot application of studies on identification, quantification (mechanisms) and prediction of transient natural hazards and associated risks.
Within NatRiskChange, a telephone aided survey was conducted in October and November 2017 among companies, which were affected from heavy rainfall or flash flood events in 2014 to 2016. We aim at gathering information about the companies experiences with severe weather warning systems, the type and extent of the damage as well es the state of recovery. Results shall identify improved mitigation measures for the management of eavy rainfall events. We thank all participants of the survey for their support!