Holocene paleo-earthquakes recorded at the transfer zone of two major faults: The Pastores and Venta de Bravo faults (Trans-Mexican Volcanic Belt)
Por:
Ortuno, M, Zuniga, FR, Aguirre-Díaz G.J., Carreón-Freyre D., Cerca M., Roverato M.
Publicada:
1 feb 2015
Resumen:
We present evidence of five late Holocene earthquake ruptures observed
at two paleo-seismological trenches in the Laguna Bani sag pond
(Trans-Mexican Volcanic Belt, central Mexico). The trenches exposed two
fault branches of the western termination of the Pastores fault, one of
the major fault systems within the central Trans-Mexican Volcanic Belt.
The site was studied by combining geomorphological and structural
approaches, volcanic mapping, ground-penetrating radar, and
paleoseismological analysis. The study revealed that coseismic surface
rupture was noncharacteristic, and that the exposed fault branches had
not always moved simultaneously. The fault tip has ruptured at least 5
times within the past 4 k.y., and the rupture events followed and
preceded the deposition of an ignimbrite. The close temporal
relationship of the seismic rupture with the volcanic activity of the
area could be the result of volcanism triggered by faulting and its
associated seismicity. The relatively high recurrence of seismic events
(1.1-2.6 k.y.) and the noncharacteristic fault behavior observed at this
tip of the Pastores fault suggest that the fault might have been active
as a primary fault rupturing along segments of variable length or depth,
and/or that the fault ruptured eventually as a secondary fault. The
secondary ruptures would likely be related to earthquakes produced at
major neighboring faults such as the Acambay fault, which moved during
the 1912 Acambay earthquake, or the Venta de Bravo fault. A relatively
large slip rate estimated for this fault branch (0.23-0.37 mm/yr) leads
us to contemplate the possible connection at depth between the Pastores
and the Venta de Bravo faults, increasing the maximum expected magnitude
for central Mexico.
Filiaciones:
Ortuno, M:
Univ Nacl Autonoma Mexico, Ctr Geociencias, Juriquilla 76230, Queretaro, Mexico
Zuniga, FR:
Univ Nacl Autonoma Mexico, Ctr Geociencias, Juriquilla 76230, Queretaro, Mexico
Aguirre-Díaz G.J.:
Univ Nacl Autonoma Mexico, Ctr Geociencias, Juriquilla 76230, Queretaro, Mexico
Carreón-Freyre D.:
Univ Nacl Autonoma Mexico, Ctr Geociencias, Juriquilla 76230, Queretaro, Mexico
Cerca M.:
Univ Nacl Autonoma Mexico, Ctr Geociencias, Juriquilla 76230, Queretaro, Mexico
Roverato M.:
Univ Nacl Autonoma Mexico, Ctr Geociencias, Juriquilla 76230, Queretaro, Mexico
All Open Access, Bronze
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