Characteristic Tectonic Tremor Activity Observed Over Multiple Slow Slip Cycles in the Mexican Subduction Zone

Abstract

We develop a single-station tremor spectrum template detection method that we applied to continuous seismic data recorded by the Mexican National Seismological Service broadband stations. This allows for an unprecedented long-term analysis of tectonic tremor in Mexico over multiple slow slip events (SSEs). We only detect tremor that are within previously discovered tremor regions, thereby extending the catalog in time but not space. The resulting catalog demonstrates the strong correlation of bursts of tremor activity and aseismic slip over multiple slow slip cycles. The M~7 long-term SSEs in the states of Guerrero and Oaxaca are associated with the longest sequences of tremor bursts. Each of these tremor bursts are made up of a series of smaller bursts. In between the large M7 SSEs, there are shorter-duration, isolated tremor bursts. In Guerrero, these shorter bursts were found to accompany M~6 short-term SSEs. The occurrence of these short-duration tremor bursts in Oaxaca demonstrates that small short-term SSEs occur in both major slow slip regions in Mexico. The discrete range of tremor burst sizes and rates suggests that slow slip events in the Mexican subduction zone are organized into characteristic moment and moment rates. The catalog also reveals other aseismic transients, such as postseismic slip in Oaxaca after the 16 February 2018 M w 7.2 Pinotepa Nacional earthquake. We highlight that such long-term catalogs are a useful tool together with geodetic observations to monitor slow slip activity that potentially plays a role in the subduction megathrust cycle.

Daily measurement of slow slip from low-frequency earthquakes is consistent with ordinary earthquake scaling

“…The 2006 M 7.5 slow slip event is an intermittent sequence of M 6 slow transients ( 12 ). The characteristic size of these slow transients echoes the recently reported characteristic rates of tectonic tremor activity during both major and small slow slip events ( 23 ). The magnitude-frequency distribution of slow transients is not well represented by an earthquake-like power law and rather appears to have a characteristic size (fig.…”

Tectonic Tremors in the Northern Mexican Subduction Zone Remotely Triggered by the 2017 Mw8.2 Tehuantepec Earthquake

“…Other techniques, such as the reference spectrum method (Miyazawa 2012), might be useful for detection; however, in this case, a dense seismic network for a statistical test and a reference event are required. This situation does not mean that no transiently triggered tremors occurred in other areas because Husker et al (2019) found clear signs of tremor burst, particularly in Oaxaca subsequent to the 2017 Tehuantepec earthquake, and the activity might have started during the passage of the seismic waves.…”

Tectonic Tremors in the Northern Mexican Subduction Zone Remotely Triggered by the 2017 Mw8.2 Tehuantepec Earthquake

“…Other techniques, such as the reference spectrum method (Miyazawa 2012), might be useful for detection; however, in this case, a dense seismic network for a statistical test and a reference event are required. This situation does not mean that no transiently triggered tremors occurred in other areas because Husker et al (2019) found clear signs of tremor burst, particularly in Oaxaca subsequent to the 2017 Tehuantepec earthquake, and the activity might have started during the passage of the seismic waves.…”

“…The 2017 Tehuantepec earthquake occurred at 04:49:46.7 on September 8, 2017 (UTC) (global centroid moment tensor (CMT) catalog), in the southern Mexican subduction zone with a mechanism of normal faulting within the Cocos Plate and ruptured the whole thickness of the Cocos Plate down to the mantle (e.g., Melgar et al 2018;Suárez et al 2019) (Figure 1). Notably, the 2017 Tehuantepec earthquake is also known to have triggered tremors along the western coast of North America (Chao et al 2017) and activated tremors in the southern Mexican subduction zone (Husker et al 2019). In the southern Mexican subduction zone, tremors were triggered by the 2010 Mw8.1 Maule earthquake accompanied by slow slip (Zigone et al 2012).…”