| Grant number: | 14/09455-3 |
| Support type: | Scholarships in Brazil - Post-Doctorate |
| Effective date (Start): | August 01, 2014 |
| Effective date (End): | October 31, 2016 |
| Field of knowledge: | Physical Sciences and Mathematics - Geosciences - Geophysics |
| Cooperation agreement: | Coordination of Improvement of Higher Education Personnel (CAPES) |
| Principal researcher: | Marcelo Sousa de Assumpção |
| Grantee: | Hans Alex Agurto Detzel |
| Home Institution: | Instituto de Astronomia, Geofísica e Ciências Atmosféricas (IAG). Universidade de São Paulo (USP). São Paulo , SP, Brazil |
| Associated scholarship(s): | 14/26330-0 - Source characterization of induced seismicity in Bebedouro, Brazil, and deep earthquakes in South America, BE.EP.PD |
Abstract Induced seismicity is nowadays a key topic in geosciences. Usually related to water injection and mining, the last few years have seen an increase of examples of man-made earthquakes around the world. In Brazil, induced seismicity cases have been related to the impoundment of reservoirs, mainly in the north-eastern border of the Paraná basin. Although magnitudes associated to induced seismicity are usually low, its occurrence in areas not prone to natural seismicity as Brazil usually generates structural damages and serious concern in local populations which are not prepared for such phenomena. In 2003, ten water wells were dug to a depth of ~120 m in the Aparecida Farm, Bebedouro municipality, São Paulo state, Brazil for irrigation purposes. Around nine months later, a series of tremors were felt by the nearby residents which prompted the installation of a local seismic network. The earthquakes were temporally correlated to the pumping periods: during pumping, no earthquakes were registered, but during the rainy season, when no pumping was executed, the tremors restarted in annual cycles. It was concluded that water percolating from the upper aquifer (sandstone) now connected to the lower aquifer (basalt) by the opening of wells, was the cause of the tremors due to an increase of pore pressures within the critically stressed basalt layer. This example is a rare, if not unique case of induced seismicity due to naturally injected water at low pressures. The present project aims to improve the hypocentral locations and understanding of the mechanics and seismotectonics of the sequence through the determination of a 3D velocity structure, relative hypocentral determination and moment tensor inversions. We consider the hypothesis that the spatio/temporal occurrence of the seismicity might be controlled by the layers geometry and velocity anomalies, thus the importance of a detailed 3D velocity structure. Additionally, the determination of focal mechanisms will shed light on the current state of the stress field for this region. The main outcome will be peer-reviewed articles. (AU) | |