Study of Scaled Energy in Latin America

Subduction zones are regions where one tectonic plate slides beneath another. This phenomenon generates a variety of earthquakes: interplate, tsunami, intraplate, and deep earthquakes. The different types of subduction zone earthquakes exhibit variations in the frequency content of the seismic energy released (Venkataraman and Kanamori, 2004). For example, tsunami earthquakes (Kanamori, 1972) occur in the shallow portions of the subduction zone. These earthquakes are deficient in high-frequency energy; however, they release a significantly larger amount of slip compared to ordinary subduction zone earthquakes. Despite their seismological similarities, there is currently no universally accepted model that describes the structural or morphological conditions around these faults that are conducive to large tsunamis with minimal ground motion (Sallares and Ranero, 2019).

The ratio of seismic energy to seismic moment, or scaled energy, can be interpreted as the radiated energy per unit area and per unit slip on the fault plane (Izutani and Kanamori, 2001). Newman and Okal (1998) demonstrated that scaled energy, calculated from observed waveforms, is one of the most powerful discriminants for tsunami earthquakes. Tsunami earthquakes typically show scaled energy values ranging from 7x10^-7 to 3x10^-6 (Venkataraman and Kanamori, 2004).

We estimate the radiated seismic energy from teleseismic P-waves using the methodology proposed by Perez-Campos et al. (2003). We calculated the scaled energy of events near the subduction zones in Mexico, Central America, and South America. The highest scaled energy value corresponds to a normal earthquake (M_W 6.6) off the coast of Chile at a depth of 15 km (April 9th, 2001). Many strike-slip earthquakes exhibit high energy, while thrust events generally have lower values.

In the case of shallow thrust events, we observe a weak relationship between scaled energy and depth. This relationship was reported by Bilek, Lay, and Ruff (2004) for Chile, Peru, and Mexico. Additionally, we explore the relationship between scaled energy and rigidity.