P27
Identification of Possible Tsunami Earthquakes along the Mexican Subduction Zone
〇Ketzallina FLORES , Yoshihiro ITO
Tsunamiearthquakes

largeOkal (1998) demonstrated that the scaled energy

earthquakes in subduction margins accompanied by(𝐸! /𝑀" ) calculated observed waveform is one of thelarge tsunamis in which the observed tsunami heights

powerful discriminants for tsunami earthquakes.

are larger than that expected from the seismic

Tsunami earthquakes typically show the scaled energy

magnitude calculated from observed strong groundfrom 7𝑥10#$ to 3𝑥10#%

motionKanamori, 2004). For instance, the scaled energies(e.g.

Geersen,aredefined2019).

Someastsunamiearthquakes have been observed in the last few decades

were calculated as#%(Venkataraman and

1.5𝑥10#% ,0.6𝑥10#%

andwith recent seismic networks. These earthquakes share

2.6𝑥10many seismological characteristics, such as deficiency

Nicaragua (2 September 1992, MW 7.6), Java (2 Junein high-frequency energy radiated from the fault; they

1994, MW 7.8), and Peru (21 February 1996, MW 7.5),

have a significantly long source duration and a large

respectively (Venkataraman, 2002).

amount of slip near the trench.

for the recent tsunami earthquakes ofOn April 18th, 2002, an earthquake with MW 6.7

Despite their seismological similarities in theseoccurred about 55 km from the coast of Guerrero,

tsunami earthquakes, there is, however, no commonly

Mexico. The hypocenter of the earthquake was locatedaccepted model with the structural or morphologicalnear the trench of the northwest Guerrero seismic gap.

conditions around these faults, which are conducive to

Despite being relatively small in magnitude, thelarge tsunamis with no strong ground motion. As one ofearthquake has all the characteristics of a tsunami

the ideas, Sallares and Ranero (2019) proposed that aearthquake

depth-dependent upper-plate elastic property cancomprehensively calculate the scaled energy ofchange rupture property as depth. The depth of faults

moderate or large earthquakes in the Mexican

possibly controls slow and fast rupture speed andsubduction zone. We also analyze the differences in thedepletion of high-frequency energy for earthquakes atscaled energy of some events and their implications. By

the shallow domain without changing fault mechanics

examining and comparing their scaled energy, we aimthemselves.

to gain insights into the seismological characteristics ofOkal and Borrero (2011) conducted a detailed

tsunami earthquakes in this region and propose a newseismological study of the large earthquake in Colima,model of tsunami earthquakes.

[Flores,2018].

In

thiswork,

weMexico. The mainshock occurred on June 3rd, 1932,

At the moment, we have found three relevant ones.

followed by aftershocks on June 18th and 22nd of theThe first occurred on February 24th, 2020. This sharessame year. The aftershock on June 22nd generated aa similar scaled energy to tsunami earthquakes. The

more devastating tsunami than that of the mainshock

second event was on July 19th, 1997. It is thedespite having much smaller seismic magnitudes. Okal

shallowest, and its scaled energy is near the valueand Borrero (2011) suggests that this aftershock had theproposed for tsunami earthquakes. Finally, the event

characteristics of a tsunami earthquake. Newman andthat occurred on July 19th, 1997, shares many
characteristics with tsunami earthquakes.