Active faults sources for the Patzcuaro-Acambay fault system (Mexico): fractal analysis of slip rates and magnitudes M-w estimated from fault length

摘要

The Patzcuaro-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 Michoacan, 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 (M-s = 6.9) on 19 November 1912 with surface rupture, and another in Maravano in 1979 with M-s = 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 15m digital elevation model, by means of three empirical relationships. In addition, the Hurst exponent H-w and its persistence, estimated for magnitudes M-w (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 = M-w = 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 turns of their roughness (H-w = 0.7, H-w = 0.5, H-w = 0.8 respectively), showing different dynamics in seismotectonic activity and; the time domain, with a strong persistence H-w = 0.949, suggests that the period