**1. Introduction**

## **1.1 Earthquake data**

The subduction zone comprises earthquakes with focal depths down to 300 km in the Central America Isthmus, where the Cocos Plate submerges beneath the Caribbean Plate. Interface subduction earthquakes occur at shallower depths in the two plates' boundary near the trench, characterized by thrust focal mechanisms. Intraplate subduction earthquakes are deeper and characterized mainly by normal focal mechanisms. Outer rise earthquakes occur southwest of the trench due to the initial flexure of the oceanic slab, yielding a shallow normal mechanism. The slab dips an average of 450 north-east, with deeper earthquakes away from the subduction trench having offshore and inland epicenters. Correa-Mora et al. [1] suggested employing GPS measurements as a weak coupling between the Cocos and the Caribbean plates with a slip rate of about 7–8 cm/year between the two plates.

The last destructive earthquake in this seismogenic zone occurred on January 13, 2001, with an M 7.7 with its epicenter offshore El Salvador [2]. Large shocks occurred on December 19, 1862 [3] and September 7, 1915 [4] beneath the western El Salvador territory with M 8.12 and M 7.8, respectively. Ambraseys and Adams [4] reported an event dated August 6, 1942, M 8.12 beneath the western Guatemalan territory. On September 2, 1992, an M 7.6 offshore Nicaragua triggered a local tsunami [5]. On July 29, 1773, an earthquake with M 7.6 struck Guatemala [3].

We updated the homogenized moment magnitude catalog of Salazar et al. [6] using online global information as the International Seismological Centre ISC [7], the Preliminary Determination of Epicenters PDE [8], the Centroid Moment Tensor solutions [9], and detail-oriented studies for earthquake locations of large earthquakes [3, 4, 10–12]. The catalog covers the geographical window between 11 and 16.5<sup>0</sup> N and 85.5–92<sup>0</sup> . The final subduction catalog contains 2764 events covering 1609–2019 within M 5–8.12 (**Figure 1a**). Note that earthquakes from other regional seismogenic sources (e.g., volcanic chain, Guatemalan faults, and Honduran–Guatemalan Grabens) were also compiled; however, this study is devoted to only subduction events. Salazar et al. [6] present the criteria to separate upper-crustal and subduction events based on geological and focal mechanism information. We also applied the Gardner and Knopoff [14] method to extract the main events from the original catalog, eliminating the foreshocks and aftershocks. The final declustered catalog contains 889 main events. Note that the method of Gardner and Knopoff [14] calibrated their method to identify aftershocks; however, it has also been applied to eliminate foreshocks with the same temporal and spatial windows of the former (e.g., [15–17]) and to assure all dependent events are removed from the catalog. About 68% of dependents' events were eliminated in the decluster process (**Figure 1b**). **Figure 2** shows a hypocenter cross-section for El Salvador and the USGS subduction slab 2.0 model [13]. The depth determination in the Central America Isthmus gives significant uncertainty; however, the USGS slab model generally depicts a reasonable top slab geometry when compared with our hypocentral determinations.

It is necessary to investigate the year of completeness for the magnitudes, especially because small events are not listed in the catalog for early years. We present in **Table 1** the year of completeness of the subduction catalog for several magnitude bins after applying the Tinti and Mulargia [18] method for both the clustered and the declustered catalog after applying the Gardner and Knopoff [14] method; **Figure 3** shows an example of completeness analysis for the magnitude bin 5.0–5.5, suggesting that the catalog entirely lists events from the year 1975 to 2019.

Salazar [16] studied the earthquake interoccurrence times and seismic hazards for earthquakes related to another seismogenic zone, namely, the upper-crustal volcanic chain in El Salvador. This work extends the former article by employing data from the overall subduction zone and studying the interoccurrence times based on the Weibull and Poisson cumulative probability distributions.
