David A. Novelo-Casanova

Comparison of techniques that use the single scattering model to compute the quality factor Q from coda waves

Using simulated coda waves, the resolution of the single-scattering model to extract codaQ (Qc) and its power law frequency dependence was tested. The back-scattering model ofAki andChouet (1975) and the single isotropic-scattering model ofSato (1977) were examined. The results indicate that: (1) The inputQc models are reasonably well approximated by the two methods; (2) almost equalQc values are recovered when the techniques sample the same coda windows; (3) lowQc models are well estimated in the frequency domain from the early and late part of the coda; and (4) models with highQc values are more accurately extracted from late code measurements.

Spatial analysis of the level of exposure to seismic hazards of health facilities in Mexico City, Mexico

To determine the level of exposure of hospitals to seismic hazards in Mexico City, Mexico, we analysed their geographic location with respect to the seismic response of the different types of local soil to which these installations are located. Hospitals were converted from a database of names and locations into a geographical information system (GIS) map layer of resources. This resource layer was superimposed with other GIS layers of seismic microzonation of Mexico City to identify those hospitals that may be threatened by a local large earthquake. We found that about 50% of the main public and 40% of the private health facilities are highly exposed. Approximately 56% of public and 44% of theprivate reference hospitals are located in soils with high seismic wave amplification properties. In a disaster situation, the best areas to set up temporary medical facilities are in those districts in Mexico City for which main and secondary transportation routes were identified with low level of exposure to seismic hazards (Alvaro Obregón, Milpa Alta, Tlalpan, Magdalena Contreras and Cuajimalpa). Our results will support decision makers in Mexico City in the development of a comprehensive seismic hazard mitigation and prevention program of health facilities including response planning.

Times of increased probability of large earthquakes (Ms ≥ 7.5) along the Mexican subduction zone

Abstract Using the method of pattern recognition of infrequent events, we explore the possibility of identifying the times of increased probability (TIP) of occurrence of large earthquakes (Ms ≥ 7.5) along the Mexican subduction zone. A TIP refers to a 5 year period within which a strong earthquake has a high probability of occurrence. We analyzed the seismicity for the regions of Chiapas-Eastern Oaxaca (91–97°W, Region 1), Western Oaxaca-Guerrero (97–102°W, Region 2), and Michoacan-Colima-Jalisco (102–106°W, Region 3) for the time interval 1970–1991 with the National Oceanic and Atmospheric Administration seismic catalog as the source data. The premonitory intermediate-term seismic activation to identify a TIP was measured using the algorithm M8. Three out of the five earthquakes of Ms ≥ 7.5 that occurred during the studied period are diagnosed by algorithm M8, and for the Region 3 segment a TIP is identified that will end between 1994 and 1996. We consider the area between the Western Colima gap and the Jalisco region (103.7–106.0°W) as the zone where the forecast earthquake has a higher than usual probability of occurrence. Our results by no means constitute a definitive earthquake prediction but suggest the need for detailed seismic analysis and the study of other geophysical precursors along the Colima-Jalisco segment.

Exposure of main critical facilities to natural and man-made hazards in Grand Cayman, Cayman Islands

The level of exposure to the impact of natural and man-made hazards of the main critical facilities at Grand Cayman (GC), Cayman Islands, was determined using the methodology developed by the National Oceanic and Atmospheric Administration Coastal Services Center. Previous studies identified hurricanes as the most important natural hazard for GC. However, other hazards include earthquakes, tsunamis and explosions or leaks of fuel storage tanks. Our results indicate that: (1) About 82% of the emergency response infrastructure, 95% of the government facilities, and 85% of the utilities have a level of exposure from low to moderate; (2) only 12% of all identified critical facilities at GC are highly exposed; (3) large explosions or leaks of the Airport Texaco Fuel Depot, the local fuel pipeline, and the Home Gas Terminal could impact nearby critical infrastructure. The facilities identified with a high level of exposure are as follows: the Bodden Town Clinic and Police Station, the West Bay Fire Station, the Georgetown Dock and Port, and the Esso and Texaco Fuel terminals. Most portions of the coastal roads are moderately exposed to natural and man-made hazards. The most exposed sections are four short segments of the road system located along the North Sound, Little Sound and Eastern West Bay area. In some cases, the high exposure of critical facilities stems from their location on the coastline. In other cases, however, adequate policies to either protect or to relocate these facilities would help to reduce their level of exposure to both natural and man-made hazards.

Flood risk assessment. Case of study: Motozintla de Mendoza, Chiapas, Mexico

ABSTRACT Due to its geographical location, the community of Motozintla de Mendoza (Motozintla) in the State of Chiapas, Mexico, is continuously exposed to the impact of natural hazards. In this work, we assessed the flood risk of Motozintla considering the structural, socioeconomic, organizational, and global (structural, socioeconomic, and organizational) vulnerabilities. In addition, we also measured the local risk perception. Spatial maps were generated to determine the most vulnerable and risk areas of this community. Our results indicate that the population has a high level of risk to flooding mainly because (1) the majority of the local houses has high structural vulnerability; (2) a high percentage of the families has a daily income less than the official Mexican minimum wage and lacks of basic public services as well as of proper social security services; (3) most of the community does not know any existing Civil Protection Plan; and (4) the community organization for disaster mitigation and response is practically non-existent. For these reasons, we believe that it is necessary for local authorities to establish in the short-term, preparedness, mitigation and response plans as well as land-use measures to reduce the risk to floods in Motozintla.

Physical vulnerability of critical facilities in Grand Cayman, Cayman Islands

Using the methodology developed by the North Carolina Department of Environment and Natural Resources, USA, we determined the physical vulnerability to the impact of hazards of the main critical facilities at Grand Cayman (GC), Cayman Islands. Our results indicate that: 1) About 82% of the emergency response infrastructure, 95% of the government facilities, and 85% of the utilities have physical vulnerabilities in the range from low to moderate; 2) Only 12% of all identified critical facilities at GC are exposed to natural and man-made hazards with a high vulnerability; 3) GC shows a very good level of protection of its critical facilities to natural hazards; 4) Explosions or leaks of the Airport Texaco Fuel Depot and the fuel pipeline, could impact the George Town Red Cross Building, the Caribbean Utilities and the Owen Roberts International Airport. An explosion of the Home Gas Terminal could damage the John Gray High School, which is also used as shelter in case of emergencies.