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Zusammenfassung:
The Trans-Mexican Volcanic Belt (TMVB) is an
active volcanic chain being deformed by an
intra-arc extensional fault network. Although
several crustal earthquakes with magnitude>7
have originated in the TMVB since the 16th
century, the background seismicity of this
geological structure is very low and the region
is usually considered of low seismic hazard. In
this study, we present an updated probabilistic
seismic hazard model of the TMVB. The
seismicity catalog used here includes forty-
three historically and instrumentally recorded
earthquakes, from 1858 to 2014; five of these
are large earthquakes that occurred in the TMVB
during the XIXth century. Due to the lack of a
statically representative sample, we propose, in
a qualitative manner, the seismicity catalog is
complete for M≥4 since 1964 and for M≥6 since
1858. Moreover, we introduce three different
earthquake frequency-magnitude relations. The
first one is a conventional Gutenberg Richter
fit of the distribution of the instrumentally
recorded earthquakes data. The other two are
non-conventional, semi-parametric approaches
that integrate the historical and the instrumental
data to determine seismicity rates in the
region. Our preferred model (seismicity model
B) fits separately the instrumental and the
historical data and merge the two fits into one
curve. A uniform seismic hazard (USH) of the
TMVB for a return period of 500 years was
calculated considering three major sources of
earthquakes: 1) Subduction thrust-faulting
events in the Middle American Trench (MAT);
2) Earthquakes within the subducted Cocos
plate and, 3) Shallow crustal earthquakes in the
TMVB. According to the seismicity model B, the
average recurrence time of a M≥7 earthquake
on the TMVB is approximately 150 years. In
contrast, the recurrence time estimated from the
instrumental catalog is 12,000 years. The results
of this seismicity model, which is based on
historical and instrumental data, agrees also with
the return periods of prehistoric earthquakes,
estimated for short segments of the fault system
in the TMVB in paleoseismological studies.
When comparing the results of our preferred
seismicity model, the PGA estimated using
only the instrumental seismicity are 18 to 56%
smaller than those predicted by the model using
the historical catalog.