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 $M 7$ 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.