Fig 1.
Map of the region under study.
JB indicates de Jalisco Block. Ellipses mark the areas of maximum damage observed during the 1568 and 1875 earthquakes and the 1912 earthquake sequence. Red stars are major earthquakes in 1932. Red circles are the earthquakes analyzed in the present study. Green circles are epicenters of the 1997 earthquake sequence. Triangles are active volcanoes. Line segments are faults and fractures. Blue and bold dashed lines are the Middle America Trench and the Trans-Mexican Volcanic Belt limit, respectively.
Fig 2.
Relocation of the studied earthquakes.
The map shows with shading the Guadalajara metropolitan area. Open red circles are the epicenters and the fault plane solutions of the earthquakes analyzed. Focal spheres contain the nodal planes of the preferred solutions with the minimum RMS errors. The numbers correspond to the events listed in Table 1. The overall seismic activity (4.0 ≤ M ≤ 4.5) for the 2006–2016 period as reported by the Servicio Sismologico Nacional of Mexico (SSN) is shown with black open circles. VT is the Tequila volcano. JO, TL, ZA, SC and ZAC are the Jocotepec, Tlaquepaque, Zapopan, San Cristobal and Zacoalco towns respectively. BS is the Barranca de Santiago. TMVB marks the limit of the Trans-Mexican Volcanic Belt. The black square shows the position of the temporary seismic station in operation from 2015 to 2016. Events 1 and 6 are the larger-magnitude earthquakes of the analyzed sequence.
Table 1.
List of analyzed earthquakes.
Table 2.
Fault plane solution parameters as obtained from the inversion.
Fig 3.
Seismic tensor inversion for Event 1.
Plot of original filtered (0.01–0.1 Hz) and instrument-corrected data compared to the synthetic seismograms. Model and observed signals are shown with red and black lines, respectively. Station and component codes are shown in the first and second columns, respectively. RRZ is the vertical component. The original horizontal component seismograms (N-S and E-W) are rotated to obtain the radial (RRR) and transversal (RRT) components shown in the figure. For display reasons, the data are autoscaled, and in the right column, the amplitudes of the observed and synthetic signals are shown. The nearest station, CJIG, is 185 km from the epicenter, and ZIIG, the farthest, is 364 km from the epicenter.
Fig 4.
Seismic tensor inversion for Event 2.
Theoretical and observed signals are shown with red and black lines, respectively. The inversion was carried out with four broadband stations. The nearest station, CJIG, is 218 km from the epicenter, and MMIG, the farthest, is 285 km from the epicenter. Other labels are as in Fig 3.
Fig 5.
Seismic tensor inversion for Event 6.
Theoretical and observed signals are shown with red and black lines, respectively. The inversion was carried out with four broadband stations. The nearest station, ANIG, is 108 km from the epicenter, and DMIG is the farthest at 467 km from the epicenter. Other labels are as in Fig 3.
Fig 6.
T-axes of the earthquakes analyzed are shown with black arrows. The preferred nodal planes are shown with red lines. The large arrow marks the approximate direction of the JB motion.