Abstract. The Pátzcuaro–Acambay fault system (PAFS), located in the
central part of the Trans-Mexican Volcanic Belt (TMVB), is delimited by an
active transtensive deformation area associated with the oblique subduction
zone between the Cocos and North American plates, with a convergence speed of
55 mm yr−1 at the latitude of the state
of Michoacán, Mexico. Part of the oblique convergence is transferred to
this fault system, where the slip rates range from 0.009 to 2.78 mm yr−1.
This has caused historic earthquakes in Central Mexico,
such as the Acambay quake (Ms=6.9) on 19 November 1912 with surface
rupture, and another in Maravatío in 1979 with Ms=5.6. Also,
paleoseismic analyses are showing Quaternary movements in some faults, with
moderate to large magnitudes. Notably, this zone is seismically active, but
lacks a dense local seismic network, and more importantly, its neotectonic
movements have received very little attention. The present research
encompasses three investigations carried out in the PAFS. First, the
estimation of the maximum possible earthquake magnitudes, based on 316 fault
lengths mapped on a 15 m digital elevation model, by means of three
empirical relationships. In addition, the Hurst exponent Hw and its
persistence, estimated for magnitudes Mw (spatial domain) and for
32 slip-rate data (time domain) by the wavelet variance analysis.
Finally, the validity of the intrinsic definition of active fault proposed
here. The average results for the estimation of the maximum and minimum
magnitudes expected for this fault population are 5.5≤Mw≤7.
Also, supported by the results of H at the spatial domain, this
paper strongly suggests that the PAFS is classified in three different zones
(western PAFS, central PAFS, and eastern PAFS) in terms of their roughness
(Hw=0.7,Hw=0.5,Hw=0.8 respectively), showing different dynamics in
seismotectonic activity and; the time domain, with a strong
persistence Hw=0.949, suggests that the periodicities of slip rates are
close in time (process with memory). The fractal capacity dimension (Db)
is also estimated for the slip-rate series using the box-counting
method. Inverse correlation between Db and low slip-rate concentration
was observed. The resulting Db=1.86 is related to a lesser concentration
of low slip-rates in the PAFS, suggesting that larger faults accommodate the
strain more efficiently (length ≥3 km). Thus, in terms of
fractal analysis, we can conclude that these 316 faults are seismically
active, because they fulfill the intrinsic definition of active faults for
the PAFS.
One invariant of intrinsic shape
