Portal de Periódicos da CAPES

Joint Tomographic Inversion Using First Arrivals, Moho-Reflected Phases, Local and Teleseismic Events in the Region of Arraiolos (Portugal)

2024; Springer International Publishing; Linguagem: Inglês

10.1007/978-3-031-48715-6_55

2522-8722

Ines Hamak, Piedade Wachilala, José Fernando Borges, Nuno Dias, Inês Rio, Mourad Bezzeghoud,

Geological and Geochemical Analysis

For several years, geoscientists studied the seismicity of Arraiolos (central Portugal) which shows persistent but diffuse activity. Due to the slow Iberian intraplate deformation, it is difficult to observe a correlation between earthquakes and outcropping faults which induce a complexity in the interpretation of tectonic processes hidden behind the occurrence of the observed seismic activity. To overcome this issue, the study of the variation of velocity structures within depth in three-dimensions is obtained through seismic tomography. The crustal image will help to better constrain the seismicity. As it is generally unlikely to obtain a uniform distribution of rays sampling a medium, several approaches can be followed to enhance the tomographic imaging. In order to improve the ray coverage, we add reflected PmP and SmS phases. Following the Mw4.9 magnitude earthquake (January 15th, 2018), a temporary network of 34 seismic stations [21 short-period stations (Institute Dom Luiz, IDL) and 13 broadband stations (Institute of Earth Science, ICT)] were deployed recording a number of 437 earthquakes during a period of 6 months. The additional local and teleseismic events were detected on seismograms and relocated from a set of 12 broadband stations (DOCTAR network—Deep Ocean Test Array) operating between May 2011 and September 2012. In this study, a first inversion was performed from the Arraiolos aftershock sequence, generating crustal images that covered only a small part of the area and showing a poor ray density, mainly due to the narrow distribution of hypocenters. To significantly improve the resolution of the model, additional events and seismic phases are integrated in the process with the purpose of detecting the eventual presence of blind faults, correlating velocity layers with geological units and relocating the seismic events within the crustal model. This broader approach can be applied to any region of the world.