Assessment of seismogenic potential and characterization of the seismic fault systems
The aim of the research within Component 1 is to study the area of Northern and Central Dalmatia, one of the most seismically active parts of Croatia: to describe its seismicity, to determine in as much detail as possible the 3D structure of the Earth’s crust (seismic velocities, density and attenuation) and the anatomy of the fault systems, and to understand the tectonic relations. The deployment of a dense network of seismographs and the development of a detailed 3D model of the crust will improve the accuracy of the locations of earthquake hotspots, will enable the calculation of the earthquake shaking scenario – the expected ground motion for probable future earthquakes, and the assessment of local seismic hazard.
To achieve our goals, we will buy and install 13 seismographs (with necessary IT equipment, e.g. servers, data storage, PCs, etc.) and temporarily deploy 12 seismographs from our project partners the Department of Earth Sciences of the University of Bergen. These seismic stations will transmit data in real time to servers at the Department of Geophysics of the Faculty of Science in Zagreb. On top of classical seismological instruments, we will buy and use a DAS unit (Distributed Acoustic Sensing) that transforms telecommunication fiber-optic cables into dense seismic arrays that are cost-effective – a novelty in seismological research in the last few years.
We will use this new dense seismic network to locate earthquakes in high precision by applying both standard techniques and innovative post-processing methods like cross-correlation and template matching. Applying these methods, we hope to obtain a consistent earthquake catalogue with a lower magnitude completeness threshold by a unit of magnitude and high-precision relocations to enhance catalogue homogeneity. It will enable a better understanding of seismicity in time and space, as well as further analyses of fault-zone structures in high resolution. Ultimately, all this should make future seismic hazard estimates more reliable and robust.
We will derive the shear-velocity structure of the fault zone by the highest-resolution non-linear seismic ambient noise tomography. By measuring the surface wave group and phase velocity for different wave periods and setting up a non-linear and/or stochastic inversion we will obtain the 3D S-velocity structure on a high-density grid. Starting from regional-scale 3D models of the lithosphere, we will improve the 3D model of the crust in the area.
Besides seismological work, geologists and geodynamicists from the University of Zagreb and Bergen will interpret seismic reflection profiles, geological maps, and borehole data for this area obtained in the last 40 years and stored in the Croatian hydrocarbon agency. Additional geology mapping will be done in order to explore structures not covered by the reflection data. Preexisting and newly collected seismic, geophysical and geological data will be used to define seismogenic potential of active faults. The regional and the local 3D crustal models, the high-quality seismic catalogue and knowledge of plate motion are necessary to understand the geodynamics of the area, i.e. interaction of the Adria microplate and the Dinarides.
The results of the research will be open to civil engineers, urban planners, and local governments so that they can use them when planning future projects. The planned temporary seismic network will be available to the Seismological Survey at the Department of Geophysics, Faculty of Science.
Principal investigator for the Component 1 is Assist. prof. Josip Stipčević
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