The tsunami threat on the Mexican west coast: A historical analysis and recommendations for hazard mitigation

Abstract

From an inspection of all tide gauge records for the western coast of Mexico over the last 37 years, a data base of all recorded tsunamis was made. Information on relevant historical events dating back two centuries, using newspaper archives, previous catalogs, and local witness interviews, was added to produce a catalog of tsunamis for the western coast of Mexico. A description of the 1932 Cuyutlfin tsunami is given. This is considered to be the most destructive local tsunami which has ever occurred in the region for which historical accounts are available. It was preceded by two precursor events, a not uncommon occurrence in that zone. A summary of the generation and coastal effects from the 1985 Michoacim tsunamis is also given. These Michoacfin tsunamis are the most recent local events in that zone.This information, and knowledge of local undersea faulting characteristics along the Mexican Pacific coast, leads to a clear differentiation of two zones of potential tsunami hazard: locally generated tsunamis south of the Rivera fracture, in the Cocos plate subsidence region, and remotely generated tsunamis north of this zone. Based on this zonation, two types of tsunami warning systems are proposed: real-time for the southern zone, and delayed-t/me for the northern. A description is provided of the Baja California Regional Tsunami Warning System that is presently operational in the northern zone.Several major industrial ports and tourist resort areas are located in the southern zone, and are therefore most vulnerable to local destructive tsunamis. Some of these sites represent important socioeconomic resources for Mexico, and have therefore been chosen for a vulnerability assessment and microzonation risk analysis. Land use patterns are identified, risks defined, and recommendations to minimize future tsunami impact are given. One case is illustrated.

Distribution of tsunami interevent times

“…Similarly (though occurring prior to the portion of the catalog analyzed in this study), a M w = 7.9 mainshock on June 3, 1932 in central Mexico produced two tsunamigenic aftershocks (M w = 7.8, M s = 6.9) within 20 days. The second aftershock generated a much larger local tsunami (most likely from a concomitant landslide) than either the mainshock or the first tsunamigenic aftershock [Farreras and Sanchez, 1991]. Therefore, there is a significant amount of complexity among triggered earthquakes in terms of the causative mechanism and the size of the tsunamis they generate.…”

Tsunami Source Inversion Using Tide Gauge and DART Tsunami Waveforms of the 2017 Mw8.2 Mexico Earthquake

“…The earthquake is known as the Chiapas earthquake or the Pijijiapan earthquake of 2017, and it was felt from the Oaxaca and Chiapas regions in the south to the center of Mexico in the capital. This event is the most powerful earthquake in Mexico since the 1985 Michoacan earthquake in Mexico City (Mendoza 1993) and the 1932 Jalisco earthquake (Farreras and Sanchez 1991;Ramírez-Herrera et al 2014). Along the Pacific coast of Mexico, there are two distinctly defined seismic gaps: the Tehuantepec and Guerrero gaps.…”

Mapping and historical reconstruction of the great Mexican 22 June 1932 tsunami

“…At the Hotel Madrid, located on the top of a sand dune 10 m a.m.s.l., inundation depth reached 2 m, and 2 to 3 m toward the sand dunes, 450 m inland on the main street in Cuyutlan (Farreras and Sánchez, 1991). While further inland, 720 m at the train station, inundation depth reached 1.5 m (Gaspar, 2010).…”

“…Camfield, 1994;Nott, 1997;Titov and Synolakis, 1997;EERI, 2011) The area drained in about three hours. Drainage went in two directions, one heading southeast through the beach, and the other to the sea through the estuary, southeast from Boca de Apiza (Farreras and Sánchez, 1991). This drainage most probably went through the Armería River, located 11 km southeast of Cuyutlán, because the estuary and Cuyutlán lagoon are connected by the Armería River.…”