Configuration of continental subduction beneath the Western Alps: results using forward modeling of receiver functions and gravity data
- 1Institution of Geology and Geophysics, Chinese Academy of Sciences, China (ytmao@mail.iggcas.ac.cn)
- 2University of Chinese Academy of Sciences, China
- 3Université Grenoble Alpes, Institut des Sciences de la Terre (ISTerre), 38041 Grenoble CEDEX 9, France
- 4Istituto Nazionale di Geofisica e Vulcanologia, Viale Benedetto XV 5, 16132 Genova, Italy
- 5Department of Earth and Environmental Sciences, University of Milano-Bicocca, Milan, Italy
- 6Istituto Nazionale di Geofisica e Vulcanologia, Via Donato Creti 12, 40128 Bologna, Italy
The Alpine orogeny, which was formed by subduction of the European plate beneath the Adria plate, is considered as one of the world’s foremost natural laboratories for the study of orogenic processes. In contrast to other mountain belts, the Western Alpine belt is curved and affected by three-dimensional effects. Due to differences in stress distribution and rheological properties of crustal rocks, the Moho geometry and crustal structure along different sections differ, in particular in the vicinity of the continental subduction complex.
To better understand the configuration of continental subduction along a profile that crosscuts the North-Western Alps, we combine receiver function analysis with computation of synthetic receiver functions and gravity anomaly modeling to precise the subduction structures and estimate a crustal 2D shear wave velocity and density model. Seismic data come from the CIFALPS2 (China-Italy-France Alps seismic survey) temporary experiment, which operated from 2018 to 2020. We use a 2D hybrid waveform simulation method (Zhao et al., 2008) that is reliable and efficient and has a better response to 2D structures compared to conventional 1D waveform inversion methods, in particular for the dipping Moho interface of the subduction complex. We compute synthetic receiver functions for a large set of models compatible with surface geology data, which are then processed to obtain synthetic CCP depth-migrated stacks. Furthermore, we model the Bouguer gravity data along the same profile to obtain preferred density distribution. The nature of rocks in the subduction complex can be inferred from our synthetical models.
Compared to the results of the CIFALPS profile in the Central Western Alps (Zhao et al., 2015), the subduction along the CIFALPS2 profile has a shallower dip angle, which is a significant difference between the two sections. As for velocity and density models, the two sections have a high velocity and high-density wedge in the subduction complex. We argue that the reason for the difference in crustal structures between the two sections may be related to the difference in stress distribution.
Zhao, L., et al. (2008). "A two-dimensional hybrid method for modeling seismic wave propagation in anisotropic media." Journal of Geophysical Research 113(B12).
Zhao, L., et al. (2015). "First seismic evidence for continental subduction beneath the Western Alps." Geology 43(9): 815-818.
How to cite: Mao, Y., Zhao, L., Paul, A., Solarino, S., Aubert, C., Dumont, T., Eva, E., Guillot, S., Malusà, M. G., Pondrelli, S., Salimbeni, S., and Schwartz, S.: Configuration of continental subduction beneath the Western Alps: results using forward modeling of receiver functions and gravity data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8117, https://doi.org/10.5194/egusphere-egu21-8117, 2021.
