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The use of earthquake closets in developing countries when large earthquakes strike

100%

Wyss M.

Acta Geophysica

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2019

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tom Vol. 67, no. 2

431--436

EN

Given that more than 90% of earthquake fatalities occur in rural environments, one has to rethink how to protect the population. With most rural buildings being one- and two-story dwellings, the earthquake closet (EC) offers an affordable solution as a protection unit. Two recent earthquakes with nearly 100,000 fatalities each are used for estimating the lives that could be saved and how much this would cost. The cost of constructing an EC in a single-family home is taken to be $500–$600 in developing countries. For the “statistical value of life” $1 million is used, a minimum amount given in the literature. The cost of hospitalization is derived from reports after an earthquake. The number of fatalities and injured avoided is estimated for an example earthquake each in China and Pakistan. The estimated dollar savings resulting in large earthquakes reach $18.3 billion at a cost of $1.3 billion, and $10 billion at a cost of $0.5 billion, respectively, in the two examples.

2

Seismic microzonation study for two mining cities in the SW of Kyrgyzstan

63%

Philippe R. , Wyss M.

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tom Vol. 71, no. 1

293--307

EN

Kyrgyzstan is an earthquake-prone country at the border of the Pamir Thrust, north of the active shortening structure of the Pamir Mountains and the intra-continental mountain belt of the Tian Shan further north. The region has had several M7+damaging earthquakes, which have killed thousands of people. In the West, the country is cut through by the 700-km long NW–SE Talas-Fergana active strike-slip fault system, where no major earthquakes have been observed in the last 250 years even though paleoseismic studies show the potential to produce M7.0+events. This study is the second part of a project to estimate the potential damage and losses on residential buildings as well as critical infrastructures in the case of a large earthquake in the two mining towns of Kadamjay and Aidarken in the SW of Kyrgyzstan. Microtremors were recorded on 82 sites and analyzed with the Horizontal-to-Vertical Spectral Ratio (HVSR) method. For each site, we estimate the average frequency of the clearest peak and its amplitude in the HVSR spectra to produce microzonation maps, in terms of response frequency. We further used these data for the calculation of ground shaking using a set of six seismic scenarios based on the known faults around the two towns. This approach has proved to be efficient in a country where the resources and available data are limited and when the time of investigation is short. The Kadamjay and Aidarken cities have been divided into different zones with specific predominant resonance frequency ranges, which information is useful for risk analysis, mitigation and buildings retrofit. In Kadamjay, three regions dominate which are related to the history of alluvial deposition in a series of terraces. The more elevated terrace could be the place of seismic site amplification. Aidarkan is much more homogenous in terms of thickness and type of alluvial deposits.

3

Estimated casualties in possible future earthquakes south and west of the M7.8 Gorkha earthquake of 2015

63%

Wyss M. , Chamlagain D.

Acta Geophysica

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2019

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tom Vol. 67, no. 2

423--429

EN

The 2015 M7.8 Gorkha earthquake has moved the upper, unbroken, part of the Main Himalayan Thrust (MHT) and the neighboring sections of this fault closer to failure. Using the program and data set of QLARM, which has been correct in fatality estimates of past Himalayan earthquakes, we estimate quantitatively the numbers of fatalities, injured and strongly affected people when assumed ruptures along these two sections will happen. In the Kathmandu up-dip scenario with M8.1, we estimate that more than 100,000 people may perish, about half a million may be injured, and 19 million are likely to be affected strongly, if we assume the high virtual attenuation observed for the 2015 Gorkha earthquake exists here also. Likewise, if the 100 km underthrusting segment west of Gorkha ruptures, we quantitatively estimate that 12,000–62,000 people may perish and 4 million to 8 million will be strongly affected, in a down-dip (lower half of the thrust plane) and an up-dip rupture (upper half) scenario, respectively. If the up-dip part of the MHT cannot rupture by itself, and greater earthquakes are required to generate the several meters of displacement observed in trenches across the MHT, then our estimates are minima.

4

The use of QLARM to estimate seismic risk in Kirghizstan at the regional and city scales

51%

Rosset P. , Toliss S. , Wyss M.

Acta Geophysica

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2020

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tom Vol. 68, no. 4

979--991

EN

An analysis of seismic risk using our tool QLARM has been performed for the Batken region including the cities of Aidarken and Kadamjay, 100 km SW of Osh. The damage to residential buildings and induced casualties has been estimated for a set of seismic scenarios of typical and maximum magnitude considering the existing seismicity data. Population and building datasets have been built based on up-to-date information, and for the two cities, satellite photographs and a feld survey have been used. A preliminary soil response zonation is proposed using seismic ambient noise analyses. In the investigated region, the probability of damaging earthquakes with M >6 is judged to be low because the slip accumulation rate along individual faults is only in the range of 0.01–0.3 cm/year. The amplifcation of seismic waves by soil deposits is estimated to be low; however, the proposed zonation needs to be complemented by additional seismic measurements. The calculations indicate that the combined fatalities of Kadamjay and Aidarken in a hypothetical earthquake of magnitude between 6.0 and 6.6 are fewer than 100.