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Induced earthquakes in Bebedouro, SE Brazil: seismicity, velocity structure and focal mechanisms

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)

Scientific publications
(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
DICELIS, GABRIEL; ASSUMPCAO, MARCELO; PRADO, RENATO LUIZ; AGURTO-DETZEL, HANS; BARBOSA, JOSE ROBERTO. Improving the characterization of the seismic source in Bebedouro, Parana Basin, Brazil: further evidence of seismicity triggered by hydraulic stimulation in water wells. Geophysical Journal International, v. 210, n. 2, p. 594-608, AUG 2017. Web of Science Citations: 1.
AGURTO-DETZEL, HANS; BIANCHI, MARCELO; PRIETO, GERMAN A.; ASSUMPCAO, MARCELO. Earthquake source properties of a shallow induced seismic sequence in SE Brazil. JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH, v. 122, n. 4, p. 2784-2797, APR 2017. Web of Science Citations: 2.
AGURTO-DETZEL, H.; BIANCHI, M.; ASSUMPCAO, M.; SCHIMMEL, M.; COLLACO, B.; CIARDELLI, C.; BARBOSA, J. R.; CALHAU, J. The tailings dam failure of 5 November 2015 in SE Brazil and its preceding seismic sequence. Geophysical Research Letters, v. 43, n. 10, p. 4929-4936, MAY 28 2016. Web of Science Citations: 9.

Please report errors in scientific publications list by writing to: cdi@fapesp.br.