Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Seismic Activity in Tucunduba Reservoir, Senador Sa-CE, Brazil,
  1997-1998   The Tucunduba Dam is about 290 km West of Fortaleza, Cear\'a state. The
seismic monitoring of the area, with a local network, has began on June 11,
1997, soon after the occurrence of the event with magnitude 3.2 $m_b$ on June
09, 1997. The monitoring was done with one the analogical station (used for
magnitude duration measurement and statistical control activity) and seven
digital stations. The digital stations, with three components each, were
operated from June to November 1997. In this work, the data collected during
digital monitoring was analyzed to determine hypocenters and focal mechanism.
To determine hypocenters, the HYPO71 program was used, with half-space model,
whose parameters were 5.95 km/s, for P-wave velocities, and 1.69 for the ratio
between P and S-wave velocity. The active zone was nearly 1 km length, with
depth between 4.5 and 5.2 km. With 16 events recorded in the same six stations,
we determined the direction of the fault plane (NE-SW). The fault mechanism is
strike-slip with a small normal component. The dip estimate was 65$^{\circ}$SE
with FPFIT and 80$^{\circ}$SE with FOCMEC. Preliminary estimates of maximum
horizontal compressive stress, using P-axis direction, were in accordance with
Ferreira {\it et al.}(1998). The small difference is probably due to influence
of the sedimentary basin in the regional stress. The active area is in
accordance with seismicity described by Assump\c{c}\~ao (1998), i. e., the
combination regional stress, local flexural effect from thick sedimentary
loads, and a presumably weaker crust from Mesozoic thinning.

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The categories of this paper are: hep-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: plasm-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: chao-dyn
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The categories of this paper are: ao-sci
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The categories of this paper are: chem-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: q-alg
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The categories of this paper are: supr-con
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The categories of this paper are: adap-org
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The categories of this paper are: cmp-lg
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The categories of this paper are: solv-int
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The categories of this paper are: mtrl-th
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The categories of this paper are: hep-ex
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The categories of this paper are: math