Spatiotemporal Variations in Slow Earthquakes Along the Mexican Subduction Zone

Abstract

Slow earthquakes in Mexico have been investigated independently in different areas. Here we review differences in tremor behavior and slow slip events along the entire subduction zone to improve our understanding of its segmentation. Some similarities are observed between the Guerrero and Oaxaca areas. By combining our improved tremor detection capabilities with previous results, we suggest that there is no gap in tremor between Guerrero and Oaxaca. However, some differences between Michoacan and Guerrero are seen (e.g., SSE magnitude, tremor zone width, and tremor rate), suggesting that these two areas behave differently. Tremor initiation shows clear tidal sensitivity along the entire subduction zone. Tremor in Guerrero is sensitive to small tidal normal stress as well as shear stress, suggesting that the subduction plane may include local variations in dip. Estimation of the energy rate shows similar values along the subduction zone interface. The scaled tremor energy estimates are similar to those calculated in Nankai and Cascadia, suggesting a common mechanism. Along‐strike differences in slow deformation may be related to variations in the subduction interface that yield different geometrical and temperature profiles.

Seismic Moment, Seismic Energy, and Source Duration of Slow Earthquakes: Application of Brownian slow earthquake model to three major subduction zones

“…The maximum width of the tremor zone also increases in this order, as Maury et al (2018) estimated widths of 23, 55, and 87 km, respectively. As mentioned above, among the three subduction zones, α À1 increases from Japan to Cascadia to Mexico.…”

“…This Brownian slow earthquake (BSE) model can explain several characteristics of slow earthquakes: constant seismic moment rate, constant seismic energy rate, flat velocity spectrum in a wide frequency range, diffusive migration behavior, and statistics of the tremor amplitude. The model also explains the ratios between the tremor energy and VLF seismic moment, which are between 10 À10 and 10 À9 , and shows little change among regions (e.g., Maury et al, 2018). The VLF signals hidden in a broadband seismogram can be detected by stacking the broadband records relative to the tremor timing, as demonstrated for Nankai, Japan (Ide & Tanaka, 2014;, Taiwan , Cascadia (Ide, 2016), and Mexico (Maury et al, 2016(Maury et al, , 2018.…”

“…Note that the observable seismic energy is usually limited in the tremor band, which is a part of entire energy defined in (6), and the contribution from the frequencies outside of this band may change the value by some factor. Figure 3b compares the seismic moment rate and seismic energy rate values, modified from the compilation of Maury et al (2018). These estimates are obtained from independent VLF events or the stacked VLF seismograms.…”

“…The VLF signals hidden in a broadband seismogram can be detected by stacking the broadband records relative to the tremor timing, as demonstrated for Nankai, Japan (Ide & Tanaka, 2014;, Taiwan , Cascadia (Ide, 2016), and Mexico (Maury et al, 2016(Maury et al, , 2018. The model also explains the ratios between the tremor energy and VLF seismic moment, which are between 10 À10 and 10 À9 , and shows little change among regions (e.g., Maury et al, 2018). This value, which is commonly called scaled energy (Kanamori & Heaton, 2000), is much smaller than the ratio for ordinary earthquakes of~10 À5 .…”

Detection of Low‐Frequency Earthquakes in Broadband Random Time Sequences: Are They Independent Events?

“…In the Nankai subduction zone, Takeo et al () and Ide and Yabe () demonstrated that stacking the broadband seismograms relative to the tremor timing recovers seismic signals at the typical frequencies of VLF events, which can then be utilized to determine their focal mechanisms. The same method has also been successfully applied in Taiwan (Ide et al, ), Cascadia (Ide, ), and Mexico (Maury et al, , ). A similar strategy has been employed for tremor bursts and SSEs.…”