Tsunami flooding extension for coastal zones of Mexico

Abstract

Joint probabilities of runup height due to astronomical tides and tsunamis are calculated for five bays on the Pacific Ocean coast of Mexico. Runup heights equaled or exceeded on the average of once per 100 years, and once per 200 years, for those bays, are evaluated. Calculations are based on wave height probabilities obtained from sets of harmonic constituents and tsunami heights recorded during the last 28 years at tidal stations on each location.

Extension of potential tsunami terrestrial flooding for populated coastal zones around those bays can be determined from the previous results. One case is illustrated showing endangered features in the hazardous zones, and recommendations to prevent casualties and property damages are given.     

Seismic and Meteorological Tsunami Contributions in the Manzanillo and Cabo San Lucas Seiches of September 14, 1995

Seismic generated sea waves from the September 14, 1995, Mexico earthquake are favored over the waves generated by hurricane Ismael to be the cause of the increase in seiche amplitudes in Manzanillo and Cabo San Lucas tide stations. The arguments are based on travel time computations from the seismic source and the moving meteorological source. A relatively sudden increase in seiche amplitudes is consistent with the arrival time of the seismic tsunami, and previously existent background is likely produced by incoming waves from the hurricane.     

Seismic and Meteorological Tsunami Contributions in the Manzanillo and Cabo San Lucas Seiches of September 14, 1995

Seismic generated sea waves from the September 14, 1995, Mexico earthquake are favored over the waves generated by hurricane Ismael to be the cause of the increase in seiche amplitudes in Manzanillo and Cabo San Lucas tide stations. The arguments are based on travel time computations from the seismic source and the moving meteorological source. A relatively sudden increase in seiche amplitudes is consistent with the arrival time of the seismic tsunami, and previously existent background is likely produced by incoming waves from the hurricane.     

Steps Towards the Implementation of a Tsunami Detection, Warning, Mitigation and Preparedness Program for Southwestern Coastal Areas of Mexico

The highly vulnerable Pacific southwest coast of Mexico has been repeatedly affected by local, regional and remote source tsunamis. Mexico presently has no national tsunami warning system in operation. The implementation of key elements of a National Program on Tsunami Detection, Monitoring, Warning and Mitigation is in progress. For local and regional events detection and monitoring, a prototype of a robust and low cost high frequency sea-level tsunami gauge, sampling every minute and equipped with 24 hours real time transmission to the Internet, was developed and is currently in operation. Statistics allow identification of low, medium and extreme hazard categories of arriving tsunamis. These categories are used as prototypes for computer simulations of coastal flooding. A finite-difference numerical model with linear wave theory for the deep ocean propagation, and shallow water nonlinear one for the near shore and interaction with the coast, and non-fixed boundaries for flooding and recession at the coast, is used. For prevention purposes, tsunami inundation maps for several coastal communities, are being produced in this way. The case of the heavily industrialized port of Lázaro Cárdenas, located on the sand shoals of a river delta, is illustrated; including a detailed vulnerability assessment study. For public education on preparedness and awareness, printed material for children and adults has been developed and published. It is intended to extend future coverage of this program to the Mexican Caribbean and Gulf of Mexico coastal areas.     

Post-Tsunami Field Survey Procedures: An Outline

Destructive tsunamis are infrequent comparedwith other natural disasters, andtheir evidences tend to disappear quickly.Conventional data acquisition havebeen limited in coverage and tend to beunreliable. Readily available andtransient data should be collectedby field survey teams as soon as possible.Since tsunamis are always triggered by the simultaneous or in-advanceoccurrence of another phenomena, they can be considered close to thesource as a syndrome, leaving a variety of almost simultaneous effectsat the nearby coasts. By observating the evidence left bythese local interaction effects, the surveyors should be able to identifyand evaluate at least the maximum horizontal extension and the verticalreach of the inundation. High water marks and lines of landward limitof sea grass, debris or sediment deposited, may help in this identification and measurement process.Guidelines to conduct post-tsunami field surveys and standards for theobservations have been established by the International Coordination Groupfor the Tsunami Warning System in the Pacific (ICG/ITSU) upon agreement with the scientific community. A Post-Tsunami Survey Field Guide was published by the Intergovernmental Oceanographic Commission (IOC) of UNESCO.