TDEM survey in an area of seismicity induced by water wells in Paraná sedimentary
basin, Northern São Paulo State, Brazil
Jorge Luís Porsani
a,
⁎
, Emerson Rodrigo Almeida
a
,
Cassiano Antonio Bortolozo
a
, Fernando Acácio Monteiro dos Santos
b
a
Universidade de São Paulo (USP), Instituto de Astronomia, Geofísica e Ciências Atmosféricas (IAG), Departamento de Geofísica, Rua do Matão, 1226, Butantã, 05508-090, São Paulo, Brazil
b
Center of Geophysics, Lisbon University (CGUL), Lisbon, Portugal
abstractarticle info
Article history:
Received 22 September 2011
Accepted 19 February 2012
Available online 2 March 2012
Keywords:
TDEM
Seismic activity area
Paraná Basin
Hydrogeology
São Paulo State
Brazil
This article presents TDEM results from an area with recent induced shallow seismicity. The purpose was to
do a geoelectrical mapping of sedimentary and fractured basaltic aquifers for better understanding of the
hydrogeologic setting. The study area is in the Paraná basin where flood basalts are overlain by sedimentary
units near the city of Bebedouro, northern São Paulo State, Brazil. 86 TDEM soundings were acquired in an
area of 90 km
2
in the Andes and Botafogo study areas. The soundings were chosen next to wells for calibra-
tion, and also along profiles crossing the seismically active areas. 1-D interpretation results showed the
general geoelectrical stratigraphy of this part of the Paraná basin. The upper geoelectrical layer is the shallow
sedimentary aquifer (Adamantina formation) with less than 80 m thickness. The second geoelectrical layer
contains the upper basalts of the Serra Geral formation at about 60–80 m depths. A saturated fractured basalt
zone between 100 and 300 m depths was identifiable on various TDEM soundings. This depth range corre-
sponds to the range of hypocentral depths for more than 3000 micro-earthquakes in this area. The lower
basalt layer was estimated to lie between 400 and 650 m depth. The deepest geoelectrical layer detected
by various TDEM soundings corresponds to the Botucatu sandstone (Guarani aquifer). Results suggest that
the high-discharge wells are located in the fractured zone in the middle basalt of the Serra Geral formation.
There is a good correlation between seismically active areas, high discharge wells (>190 m
3
/h), and fracture
zones in the middle basalt. The results reinforce the hypothesis that the shallow seismic activity in the
Bebedouro region is being triggered by high rates of groundwater withdrawal.
© 2012 Elsevier B.V. All rights reserved.
1. Introduction
The Time Domain ElectroMagnetic (TDEM) method is relatively
new, when compared with frequency-domain electromagnetic resis-
tivity methods. TDEM was introduced for ground water exploration
in the mid-1980s where there was a need for deep exploration in
the presence of low resistivity layers. In that environment, frequency-
domain methods were not able to achieve adequate depth or resolution
(Christiansen et al., 2006). Since the 1980s, TDEM data acquisition
and processing techniques have been steadily developing, and have
been applied in various countries (Bortolozo et al., 2010; Monteiro
Santos and El-Kaliouby, 2011; Porsani et al., 2012; Sørensen et al.,
2003 among others).
The history of TDEM applications for hydrogeological studies has
shown that it is a robust geophysical method with a fast data acquisi-
tion, and the results usually have good correlation with geological
information from adjacent water wells. Because of its utility for
geoelectrical stratigraphy, the TDEM method is an excellent tool for
mapping sedimentary basins, groundwater and mineral exploration,
environmental studies, geothermal studies, brine intrusion in coastal
aquifer, etc. (Christiansen et al., 2006; Danielsen et al., 2003;
Fitterman and Stewart, 1986; Hallbauer-Zadorozhnaya and Stettler,
2009; Jørgensen et al., 2003; Krivochieva and Chouteau, 2003; Land
et al., 2003; McNeill, 1994; Nielsen et al., 2007; Sørensen et al., 2003).
Many researchers have used the TDEM successfully in hydrology
studies, but there is no record to our knowledge of using this method
in an area where seismic activity has been triggered by extraction
from water wells. Additionally, this method has only been used for
a few studies in Brazil (Bortolozo et al., 2010; Carrasquila and
Ulugergerli, 2006; Lucena et al., 2009; Meju et al., 1999; Porsani
et al., 2010, 2012; Santos and Porsani, 2007), and there is certainly a
need to obtain hydrogeological information over vast tropical areas
with deeply weathered soils.
Earthquakes induced by filling of large hydroelectric reservoirs or
fluid injection under high pressure in deep wells are common phe-
nomena that have been studied in several cases (Assumpção et al.,
2002; Chimpliganond et al., 2007; Ferreira et al., 2008; Gupta, 1992;
Simpson et al., 1988; Talwani and Acree, 1984; Talwani et al., 2007,
Journal of Applied Geophysics 82 (2012) 75–83
⁎ Corresponding author. Tel.: +55 11 3091 4734; fax: +55 11 3091 5034.
E-mail addresses: porsani@iag.usp.br (J.L. Porsani), fasantos@fc.ul.pt (F.A.M. Santos).
0926-9851/$ – see front matter © 2012 Elsevier B.V. All rights reserved.
doi:10.1016/j.jappgeo.2012.02.005
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