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| Titel |
Modeling seismic wave propagation across the European plate: structural models and numerical techniques, state-of-the-art and prospects |
| VerfasserIn |
Andrea Morelli, Peter Danecek, Irene Molinari, Luca Postpischl, Renata Schivardi, Paola Serretti, Maria Rosaria Tondi |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250043488
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| Zusammenfassung |
| Together with the building and maintenance of observational and data banking infrastructures
— i.e. an integrated organization of coordinated sensor networks, in conjunction with
connected data banks and efficient data retrieval tools — a strategic vision for bolstering the
future development of geophysics in Europe should also address the essential issue of
improving our current ability to model coherently the propagation of seismic waves across
the European plate. This impacts on fundamental matters, such as correctly locating
earthquakes, imaging detailed earthquake source properties, modeling ground shaking,
inferring geodynamic processes. To this extent, we both need detailed imaging
of shallow and deep earth structure, and accurate modeling of seismic waves by
numerical methods. Our current abilities appear somewhat limited, but emerging
technologies may enable soon a significant leap towards better accuracy and reliability. To
contribute to this debate, we present here the state-of-the-art of knowledge of earth
structure and numerical wave modeling in the European plate, as the result of a
comprehensive study towards the definition of a continental-scale reference model. Our
model includes a description of crustal structure (EPcrust) merging information
deriving from previous studies – large-scale compilations, seismic prospection,
receiver functions, inversion of surface wave dispersion measurements and Green
functions from noise correlation. We use a simple description of crustal structure, with
laterally-varying sediment and cristalline layers thickness, density, and seismic
parameters. This a priori crustal model improves the overall fit to observed Bouguer
anomaly maps over CRUST2.0. The new crustal model is then used as a constraint
in the inversion for mantle shear wave speed, based on fitting Love and Rayleigh
surface wave dispersion. The new mantle model sensibly improves over global S
models in the imaging of shallow asthenospheric (slow) anomalies beneath the Alpine
mobile belt, and fast lithospheric signatures under the two main Mediterranean
subduction systems (Aegean and Tyrrhenian). We validate this new model through
comparison of recorded seismograms with simulations based on numerical codes
(SPECFEM3D). To ease and increase model usage, we also propose the adoption of a
common exchange format for tomographic earth models based on JSON, a lightweight
data-interchange format supported by most high-level programming languages, and provide
tools for manipulating and visualising models, described in this standard format, in
Google Earth and GEON IDV. In the next decade seismologists will be able to reap
new possibilities offered by exciting progress in general computing power and
algorithmic development in computational seismology. Structural models, still based
on classical approaches and modeling just few parameters in each seismogram,
will benefit from emerging techniques – such as full waveform fitting and fully
nonlinear inversion – that are now just showing their potential. This will require
extensive availability of supercomputing resources to earth scientists in Europe,
as a tool to match the planned new massive data flow. We need to make sure that
the whole apparatus, needed to fully exploit new data, will be widely accessible.
To maximize the development, so as for instance to enable us to promptly model
ground shaking after a major earthquake, we will also need a better coordination
framework, that will enable us to share and amalgamate the abundant local information
on earth structure — most often available but difficult to retrieve, merge and use.
Comprehensive knowledge of earth structure and of best practices to model wave propagation
can by all means be considered an enabling technology for further geophysical
progress. |
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