Seismic zones: The intertwined dynamics of the main fault plane and its host medium – INTERTWINE

Over the past decades, it has become clear that the deadliest and the costliest earthquakes are related to poor hazard assessment. Understanding what is an earthquake, when and where it may strike is a fundamental step to mitigate seismic risk all over the world. To be predictive, two pieces of information are compulsory: we need to know the physical properties of the fault and how much energy, ready to be released seismically, is stored in the surrounding rocks.
While, since the 1960’s, a thorough effort has been made to understand the frictional behavior of faults in the brittle crust, surprisingly very little has been undertaken to assess the energy build up and how it may vary through time. Indeed, in seismotectonics, out of simplicity, the host medium is considered elastic, i.e. it never evolves. Yet geological and geophysical observations of fault zones tell a different story. They suggest that on top of the ``seismic cycle” there is a superimposed ``cycle” where the properties of the surrounding rocks evolve according to the fault slip dynamics. Hence, in turn, it influences how much energy can be stored and how it is released (seismically or aseismically). Yet, the models we use nowadays do not take into account this INTERTWINEd dynamics.
To fully address this shortcoming, a multidisciplinary approach is necessary. I propose to develop the next generation of models that will account for this variation of energy build up over the seismic cycle. I will bring a particular attention on off-fault fracture growth and healing, and on fluids circulation. Conjointly, acquisition of geodetic and field data will help to constrain and cross-validate the numerical models. For accessibility, we will focus on continental faults in Taiwan, India and USA.
For too long, communities have been analyzing the same problem separately. Upon completion, this project will provide a unified framework to study active fault zones and provide a physics-based tool to assess seismic risk.