Geohazards: From process understanding to quantifying extremes

Understanding the natural processes and their interactions with human activities that may lead to disasters is a prerequisite for the design of mitigation measures. Closing the gaps in process understanding and integrating process knowledge in hazard assessment will allow funds for disaster mitigation to be allocated more efficiently, leading to a reduction in losses.
Extreme events are understood as those that are rare, or that may have grave consequences for society. Reliable quantification of extremes is therefore a particular scientific challenge. Since the observation of extremes is hampered by their rarity or singularity, process understanding is essential for hazard and risk assessment. The goal of this subtopic is to advance the methods for the quantification of the occurrence, intensity and extent of extremes due to natural phenomena such as earthquakes, tsunamis, and volcanic eruptions. A thorough understanding of the natural processes that may lead to extremes improves hazard assessment, assist with the derivation of realistic worst-case scenarios and upper bounds, and helps to design adequate mitigation measures. The activities in this subtopic, therefore, cover aspects of geohazards that reach from the understanding of the processes involved to the quantification of extremes.

1.1 Physics of earthquakes
Understanding and quantifying the physical processes involved in nucleation, rupture initiation and propagation of earthquakes, and knowing how these processes are related to the complexity of fault systems belong to our major scientific objectives within the research field “physics of earthquakes”.

1.2 Physics of volcanic processes
The physical processes acting during volcanic crisis and eruptions are studied by means of field- and satellite-based techniques, as well as experimental and theoretical modelling. Activity changes at volcanoes are analyzed geodetically and seismically as a function of time, and by using computer simulations an indirect view into the volcano and its magma physics is obtained.

1.3. Earthquake hazard assessment
A particular challenge will be transferring improved process understanding into practical hazard assessment. In the case of quantifying the seismic hazard, for instance, more realistic models of stress transfer in the lithosphere/asthenosphere system will allow us to move from time-independent hazard estimates to time-dependent estimates that additionally take into account the development of stress at a particular fault system.

1.4 Earthquake microzonation
Seismic hazard assessment requires knowledge not only of the earthquake sources and propagation of seismic waves, but also of the effect of local geology on earthquake ground shaking.