Miguel A. Jaimes

COMPARISON OF METHODS TO PREDICT RESPONSE SPECTRA AT INSTRUMENTED SITES GIVEN THE MAGNITUDE AND DISTANCE OF AN EARTHQUAKE

We compare four methods, all based on Bayesian regressions, to predict response spectra at instrumented sites, located at the hill and lakebed zones in Mexico City, that have recorded several recent earthquakes. The regressions are built as functions of magnitude and closest distance to the rupture area of the earthquake, using more than 20 subduction earthquakes (thrust-faulting mechanism) recorded since 1964. The four methods are: (1) a regression on observed response spectra; (2) a regression on observed Fourier amplitude spectra and use of random vibration theory to estimate the response spectra, (3) a regression on observed response spectra at the reference hill-zone station multiplied by response spectral ratios; and (4) a regression on Fourier amplitude spectra at the reference hill zone, multiplied by Fourier spectral ratios and use of the random vibration theory to estimate response spectra.

Event-based approach for probabilistic flood risk assessment

ABSTRACT An event-based approach for probabilistic flood risk assessment for financial and civil protection applications is proposed. The risk parameters are evaluated in an event-based probabilistic framework for a set of hazard events and then all these results are probabilistically integrated, including, in a formal way, all uncertainties related to each and every part of the process. The hazard is defined as a stochastic or historic set of events, collectively exhaustive and mutually exclusive, that describes the spatial distribution, the annual frequency, and the randomness of the hazard intensity. The risk is expressed in different economic terms: the average annual loss, the pure risk premium, and the loss exceedance curve. As an illustrative example, this approach is applied to Acapulco city located on the Pacific coast of Mexico. These metrics are of particular importance for risk retention (financing) schemes or risk transfer instruments, and, therefore, they will be a particularly valuable contribution to further studies in defining strategies for financial protection against disasters. With these results, further results may be obtained for civil protection and land use applications.

Seismic Vulnerability of an Inventory of Overturning Objects

A methodology is presented for assessing the probability of overturning under the action of ground motions of given intensities, and the expected values and standard deviations of damage produced by overturning of objects in a group or inventory exposed to the same seismic event. We apply this methodology to one example of the typical contents located on the base (i.e., free-field) of a middle-class house or apartment. A detailed inventory was gathered, and recent well-recorded accelerograms at the site were used to compute the rocking response of every object. Vulnerability functions for the whole inventory computed at four different sites in terms of epicentral distance and site effects show large differences between them.

Event-based approach for probabilistic agricultural drought risk assessment under rainfed conditions

An event-based approach for the probabilistic risk assessment of agricultural drought under rainfed conditions to estimate the economic impact is proposed. The risk parameters are evaluated in an event-based probabilistic framework for a set of hazard events; these results are probabilistically integrated including, in a formal way, all uncertainties related to every part of the process. The hazard is defined as a stochastic or historic set of events, collectively exhaustive and mutually exclusive, that describes the spatial distribution, the annual frequency, and the randomness of the hazard intensity. The risk is expressed in different economic terms: the average annual loss (or pure risk premium) and the loss exceedance curve; these metrics are of particular importance for risk retention (financing) schemes or risk transfer instruments. As an illustrative example, this approach is applied to probabilistic drought risk assessment of maize under rainfed conditions in Mexico. These results are the base of further studies in defining strategies for financial protection against agricultural losses and disasters.

Ground-Motion Prediction Model From Intermediate-Depth Intraslab Earthquakes at the Hill and Lake-Bed Zones of Mexico City

We present ground-motion prediction equations, based on Bayesian regressions, to predict response spectra at sites located within the hill and lake-bed zones of Mexico City for intermediate-depth, normal-faulting intraslab earthquakes with magnitude ranges 5.2 ≤ Mw ≤ 7.4; distances from sites to the fault surface 103 ≤ R ≤ 464 km; and focal depths of the events 40 ≤ H ≤ 128 km, all at sites located in hill and lake-bed zones in Mexico City. The equations are built as functions of magnitude and distance to the fault surface, using more than 20 intraslab earthquakes. We compare our results with previous attenuation models for intraslab (hill zone) and interplate earthquakes (hill and lake-bed zones) in Mexico City. The results also show that the uncertainty for intraslab earthquakes at sites located within the hill zone is larger than that for sites located in lake-bed zone.

Risk Analysis for Structures Exposed to Several Multi-Hazard Sources

A criterion for the estimation of losses of a structure exposed to several hazards is presented. It includes an approach to estimate the probability density function of the total damage that may be generated by the superposition of the effects of several simultaneous hazardous events that can be associated with a main primary event. It considers the probabilistic correlation of damage or failure of a structure due to the combined action of those simultaneous associated hazards. Finally, the intensities and times of occurrence of all relevant events of different natural origin that may significantly contribute to the risk for the structure of interest are taken into account, considering them as independent, with a negligible probability of producing simultaneous groups of significant associated hazardous events.

Effects of hurricane Odile on the infrastructure of Baja California Sur, Mexico

In September 2014, the state of Baja California Sur (BCS), Mexico, was struck by hurricane Odile. The hurricane caused extensive damage to the infrastructure of the state of BCS, where the energy and water supply were interrupted for several days. The direct economic impact was estimated to be more than 1654 million USD. Considering this damage, few days after the cyclonic event, a technical visit to BCS was carried out. The objective of this study is to present the relevant information on the performance of the infrastructure observed after the event, and to make recommendations in order to mitigate the effects of future cyclonic storms in Mexico, based on the observations during the technical visit. The main causes of damage were the use of materials for non-structural elements with a weak performance under high wind speeds, failures in the design and construction of connections of structural and non-structural elements, accumulated damage, lack of maintenance and impact of wind-born debris, as well as the absence of a building code in the region. Background information about meteorological and climatological aspects of the cyclones that have affected the southern region of BCS, the characteristics of hurricane Odile, the analysis of structural damages and the conclusions, are also presented.

Spectral Attenuation Relations at Soft Sites Based on Existing Attenuation Relations for Rock Sites

A simple and general method based on well-known random vibration theory is used to compute spectral attenuation relations at soft sites based on existing spectral attenuation relations at rock sites. The method consists of: (1) computation, for given magnitude and distance, of the expected Fourier amplitude spectrum associated with the median rock response spectrum computed with the attenuation relation; (2) inclusion of site effects characterized by a frequency-dependent, linear, or nonlinear transfer function; and (3) computation of the response spectrum at the soft site.

Ground‐Motion Prediction Model from Local Earthquakes of the Mexico Basin at the Hill Zone of Mexico City

Abstract We developed ground‐motion prediction equations (GMPEs) based on Bayesian regressions to predict response spectra at sites located in the hill zone of Mexico City for local earthquakes of the Mexico basin. The coefficients of the GMPEs are built as functions of magnitude (2.3≤ M w ≤3.8) and hypocentral distance (8≤ R ≤60  km), using 15 local earthquakes. We compare our results with five GMPEs, an attenuation model obtained in the northern region of the subduction zone in the Pacific coast of Mexico from small earthquakes, and four other existing GMPEs for shallow crustal earthquakes. Two of the GMPEs, although not the most recent ones, are still used to perform probabilistic seismic‐hazard analysis for the region under study.

Seismic Vulnerability of Building Contents for a Given Occupancy Due to Multiple Failure Modes

A methodology is presented for assessing the seismic vulnerability of inventories of contents to multiple failure modes. An ordering method to find out probabilities of failure of a conditional mode upon the survival of the other modes is applied. The procedure considers the statistical correlation of failure modes due to the dynamic response, such as sliding and/or overturning, of contents and also to non structural components. This methodology was applied to inventories of four types of occupancy (house, school, office, and hospital) located in Mexico City, considering that all contents are situated at ground level. Expected damage functions for these inventories show large differences between them, the house and school inventories being the least vulnerable, and the hospital inventory, the most vulnerable, even for low intensities.