{"id":6301,"date":"2017-08-22T14:22:54","date_gmt":"2017-08-22T18:22:54","guid":{"rendered":"http:\/\/latinamericasecurityreport.com\/?p=6301"},"modified":"2017-08-22T14:22:54","modified_gmt":"2017-08-22T18:22:54","slug":"a-new-map-of-seismic-hazards-in-brazil-shows-that-new-building-code-is-required","status":"publish","type":"post","link":"https:\/\/latinamericasecurityreport.com\/?p=6301","title":{"rendered":"A New Map of Seismic Hazards in Brazil Shows That New Building Code Is Required"},"content":{"rendered":"
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Survey under way seeks to help ensure earthquake-resistant construction becomes more widespread (photo: Bento Rodrigues, Mariana, MG \/ Antonio Cruz \/ Ag\u00eancia Brasil)<\/figcaption><\/figure>\n

Researchers are working on a new national map of seismic hazards for Brazil. In preparing the seismic hazard map, the researchers first conducted a survey of the tremors that have occurred in Brazil in recent decades in order to determine the level of seismic activity in each region.<\/p>\n

According to the survey, seismic events occur most frequently in the Northeast, especially in the states of Cear\u00e1 and Rio Grande do Norte, in northern parts of Mato Grosso and Goi\u00e1s states, and in Mato Grosso state\u2019s wetlands (Pantanal biome).<\/p>\n

\u201c<\/span>Actually, any region is susceptible to seismic tremors. The probability is higher in some areas, such as Minas Gerais, and lower in others. We don\u2019t yet know exactly why some areas are more active than others,\u201d said Marcelo Sousa de Assump\u00e7\u00e3o, a professor at the University of S\u00e3o Paulo\u2019s Institute of Astronomy, Geophysics &<\/span>Atmospheric Sciences (IAG<\/span>–USP<\/span>), and one of the coordinators of the Brazilian Seismographic Network (RSBR<\/span>).<\/p>\n

\u201c<\/span>Seismic risk is relatively low in Brazil compared with other South American countries, such as Chile or Peru, thanks to its location in a stable region with very old topography and in the interior of a tectonic plate,\u201d Assump\u00e7\u00e3o said.<\/p>\n

\u201c<\/span>But low-and medium-intensity tremors occur with a certain frequency in Brazil, and these can have drastic consequences depending on where they happen,\u201d said the principal investigator for the research project \u201cPantanal-Chaco-Paran\u00e1 basins (PCPB<\/span>): crust and upper mantle seismic structure and evolution\u201d, supported by the S\u00e3o Paulo Research Foundation (FAPESP<\/span>).<\/p>\n

A recent example was the series of tremors of magnitudes 2.01-2.55 that occurred in Mariana, Minas Gerais state, three days before the collapse of the Fund\u00e3o tailings dam owned by Samarco, resulting in the worst environmental disaster in Brazilian history.<\/p>\n

FAPESP<\/span> notes<\/a> that despite its low magnitude, the epicenter of a 2.5 tremor occurred only 1 km from the tailings dam, according to a statement by Samarco in a report on the causes of the accident prepared by an international committee of experts that analyzed the dam geotechnically.<\/p>\n

One of the committee\u2019s conclusions was that low-magnitude tremors cannot endanger well-built structures that are in use. \u201cThis dam, however, was in a fragile condition, and the tremors occurred an hour before it burst,\u201d Assump\u00e7\u00e3o said.<\/p>\n

Based on the frequency and magnitude of these tremors, they estimated the probability of similar tremors in the coming years and the level of vibration they would cause in the soil on which homes, hospitals, stores and other buildings stand, given their distance from the epicenter.<\/p>\n

Magnitude 3 tremors, for example, occur twice per month on average in Brazil. Magnitude 4 tremors, such as the 2012 quake in Montes Claros, Minas Gerais, occur twice a year. Magnitude 5 tremors, such as the quake that hit the town of Itacarambi in Minas Gerais in 2007, cause damage and occur once every fifty years, according to the researchers.<\/p>\n

\u201c<\/span>The tremors that occurred before the collapse of Samarco\u2019s tailings dam in Mariana, for example, occur all the time and are felt only when they occur near a town or city,\u201d Assump\u00e7\u00e3o said.<\/p>\n

\u201c<\/span>Although seismic events of this magnitude are relatively low-level, if they occur 1 km from a building or in the middle of a town, their intensity can be substantial, and they can have a serious impact on the population.\u201d<\/p>\n

He added that Brazil\u2019s seismic-resistant building standard, NBR<\/span>-15421, in force since 2006, was based on an outdated seismic hazard map. \u201cWe believe Brazil has many more earthquake-prone areas than are identified by the old map on which the standard was based,\u201d he said.<\/p>\n

Builders of hydroelectric dams are required to perform seismic hazard studies before their designs are approved. In the case of tailings dams, many mining companies perform seismic hazard studies as part of the design process to make sure they can withstand a major earthquake, but not all do so, according to Assump\u00e7\u00e3o. \u201cThere were no regulations that required seismic studies for approval of tailings dams,\u201d he said.<\/p>\n","protected":false},"excerpt":{"rendered":"

Researchers are working on a new national map of seismic hazards for Brazil. In preparing the seismic hazard map, the researchers first conducted a survey of the tremors that have occurred in Brazil in recent decades in order to determine the level of seismic activity in each region. According to the survey, seismic events occur most…<\/p>\n","protected":false},"author":124,"featured_media":6302,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"ngg_post_thumbnail":0,"fifu_image_url":"","fifu_image_alt":"","footnotes":""},"categories":[185],"tags":[],"class_list":["post-6301","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-energy-infrastructure"],"_links":{"self":[{"href":"https:\/\/latinamericasecurityreport.com\/index.php?rest_route=\/wp\/v2\/posts\/6301","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/latinamericasecurityreport.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/latinamericasecurityreport.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/latinamericasecurityreport.com\/index.php?rest_route=\/wp\/v2\/users\/124"}],"replies":[{"embeddable":true,"href":"https:\/\/latinamericasecurityreport.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=6301"}],"version-history":[{"count":1,"href":"https:\/\/latinamericasecurityreport.com\/index.php?rest_route=\/wp\/v2\/posts\/6301\/revisions"}],"predecessor-version":[{"id":6303,"href":"https:\/\/latinamericasecurityreport.com\/index.php?rest_route=\/wp\/v2\/posts\/6301\/revisions\/6303"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/latinamericasecurityreport.com\/index.php?rest_route=\/wp\/v2\/media\/6302"}],"wp:attachment":[{"href":"https:\/\/latinamericasecurityreport.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=6301"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/latinamericasecurityreport.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=6301"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/latinamericasecurityreport.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=6301"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}