Arquivo da tag: Terremotos

Previsão do clima: terremotos intermitentes (Folha de S.Paulo)

Marcelo Leite, 03/05/2015  01h57

Depois de Katmandu, o terremoto no Nepal sacudiu também uma noção preconcebida comum entre jornalistas de ciência – esta coluna, por exemplo, foi abalada por um tuíte de Matthew Shirts, que levava para uma reportagem da revista “Newsweek”.

A leitura do texto, “Mais Terremotos Fatais Virão, Alertam Cientistas da Mudança do Clima”, trouxe à memória um momento constrangedor. Que o relato sirva para desencorajar nossa tendência a acreditar em verdades estabelecidas.

Certa vez um colega de redação perguntou se eu poderia escrever para explicar por que tsunamis estavam se tornando mais frequentes e qual era a relação disso com o aquecimento global. Segurei a vontade de rir e expliquei, condescendente, que processos climáticos não tinham o poder de desencadear eventos geológicos.

Não é bem assim. Há pesquisadores respeitáveis investigando a hipótese de que a mudança climática deflagrada pelo aquecimento global possa, sim, tornar terremotos e erupções vulcânicas mais frequentes.

Não seria nada inédito na história da Terra. Um exemplo recentíssimo na escala geológica (o planeta tem mais de 4 bilhões de anos) ocorreu entre 20 mil e 12 mil anos atrás, ao término do último período glacial.

A retração de geleiras continentais com quilômetros de espessura aliviou a pressão sobre a crosta terrestre o bastante para desencadear intensa atividade vulcânica. Há boas evidências disso em lugares como a Islândia.

O geólogo britânico Bill McGuire tem uma teoria ainda mais preocupante. Ele acha que a elevação dos mares em 100 m, causada pelo derretimento das calotas de gelo, teria deflagrado também terremotos e tsunamis (o que poderia repetir-se a partir de agora, com o aquecimento da atmosfera).

O imenso volume de água adicionado aos oceanos, ao pressionar suas bordas, teria desestabilizado as falhas geológicas próximas da costa, causando os tremores e colapsos submarinos que levantam ondas colossais. Mas a hipótese de McGuire, detalhada no livro “Acordando o Gigante”, ainda carece de medições e dados para ser aceita.

No caso do terremoto de Katmandu, o mecanismo pressuposto para pôr a culpa no clima é outro: chuva. Não uma pancada qualquer, mas as poderosas monções que castigam Índia e Nepal de junho a agosto.

Tamanho volume de água, que perde só para o movimentado na bacia Amazônica, seria capaz de alterar o balanço do estresse entre as placas Indo-Australiana e Asiática. O geólogo argelino Pierre Bettinelli, então no CalTech, mostrou que a atividade sísmica nos Himalaias é duas vezes mais intensa no inverno e atribuiu isso à gangorra de pressões entre os dois lados da falha tectônica.

Falta provar, claro. Mas que é instigante, isso é.

Quanto a terremotos causados pelo aquecimento global, ninguém precisa sair comprando kits de sobrevivência. O degelo da última glaciação demorou milhares de anos, e as piores previsões para a subida no nível dos oceanos indicam não muito mais que 1 m ou 2 m até o final deste século.

Ninguém está a salvo de tsunamis, porém. Há alguma chance – uma vez a cada 10 mil anos, talvez – de que o litoral brasileiro seja atingido por um deles, como pode ter ocorrido com São Vicente em 1541, após cataclisma nalgum ponto do Atlântico.

Anúncios

Alteração comportamental de animais sinaliza, dias antes, a ocorrência de terremotos (Pesquisa Fapesp)

27 de abril de 2015

Estudo realizado no Parque Nacional Yanachaga, no Peru, correlacionou mudanças de comportamento de aves e pequenos mamíferos com a ionização da atmosfera causada pelo atrito subterrâneo das rochas (roedor paca [Cuniculus paca] filmado por uma camera tipo ‘motion-triggered’ / foto TEAM Network; teamnetwork.org)

José Tadeu Arantes | Agência FAPESP – O dado de que alterações no comportamento dos animais sinalizam, com horas ou dias de antecedência, eventos como os terremotos já era conhecido. Especialmente noticiada foi a disparada dos elefantes asiáticos para terras altas por ocasião do terremoto seguido de tsunami de 26 de dezembro de 2004. Muitas vidas humanas foram salvas graças a isso. Mas tais eventos ainda não haviam sido documentados de maneira rigorosa e conclusiva. Nem fora estabelecida uma correlação de causa e efeito entre essa modificação do comportamento animal e fenômenos físicos mensuráveis.

Isso ocorreu agora em pesquisa realizada por Rachel Grant, da Anglia Ruskin University (Reino Unido), Friedemann Freund, da agência espacial Nasa (Estados Unidos), e Jean-Pierre Raulin, do Centro de Radioastronomia e Astrofísica Mackenzie (Brasil). Artigo relatando o estudo, “Changes in Animal Activity Prior to a Major (M=7) Earthquake in the Peruvian Andes”, foi publicado na revista Physics and Chemistry of the Earth.

O físico Jean-Pierre Raulin, professor da Universidade Presbiteriana Mackenzie, participou do estudo no contexto do projeto de pesquisa “Monitoramento da atividade solar e da Anomalia Magnética do Atlântico Sul (AMAS) utilizando uma rede de receptores de ondas de muita baixa frequência (VLF) – SAVNET – South América VLF network”, apoiado pela FAPESP.

“Nosso estudo correlacionou alterações no comportamento de aves e pequenos mamíferos do Parque Nacional Yanachaga, no Peru, com distúrbios na ionosfera terrestre, ambos os fenômenos verificados vários dias antes do terremoto Contamana, de 7,0 graus de magnitude na escala Richter, que ocorreu nos Andes peruanos em 2011”, disse Raulin à Agência FAPESP.

Os animais foram monitorados por um conjunto de câmeras. “Para não interferir em seu comportamento, essas câmeras eram acionadas de forma automática no momento em que o animal passava na sua frente, registrando a passagem por meio de flash de luz infravermelha”, detalhou o pesquisador. Em um dia comum, cada animal era avistado de cinco a 15 vezes. Porém, no intervalo de 23 dias que antecedeu o terremoto, o número de avistamentos por animal caiu para cinco ou menos. E, em cinco dos sete dias imediatamente anteriores ao evento sísmico, nenhum movimento de animal foi registrado.

Nessa mesma época, por meio do monitoramento das propriedades de propagação de ondas de rádio de muito baixa frequência (VLF), os pesquisadores detectaram, duas semanas antes do terremoto, perturbações na ionosfera sobre a área ao redor do epicentro. Um distúrbio especialmente grande da ionosfera foi registrado oito dias antes do terremoto, coincidindo com o segundo decréscimo no avistamento dos animais.

Os pesquisadores propuseram uma explicação capaz de correlacionar os dois fenômenos. Segundo eles, a formação maciça de íons positivos, devido à fricção subterrânea das rochas durante o período anterior ao terremoto, teria provocado tanto as perturbações medidas na ionosfera quanto a alteração comportamental dos animais. A fricção é resultado da subducção ou deslizamento da placa tectônica de Nazca sob a placa tectônica continental.

É sabido que a maior concentração de íons positivos na atmosfera provoca, seja em animais, seja em humanos, um aumento dos níveis de serotonina na corrente sanguínea. Isso leva à chamada “síndrome da serotonina”, caracterizada por maior agitação, hiperatividade e confusão. O fenômeno é semelhante à inquietação, facilmente perceptível em humanos, que ocorre antes das tempestades, quando a concentração de elétrons nas bases das nuvens também provoca um acúmulo de íons positivos na camada da atmosfera próxima ao solo, gerando um intenso campo elétrico no espaço intermediário.

“No caso dos terremotos, cargas positivas formadas no subsolo devido ao estresse das rochas migram rapidamente para a superfície, resultando na ionização maciça de moléculas do ar. Em algumas horas, os íons positivos assim formados alcançam a base da ionosfera, localizada cerca de 70 quilômetros acima do solo. Esse aporte maciço de íons teria provocado as flutuações da densidade eletrônica na baixa ionosfera que detectamos. Por outro lado, durante o trânsito subterrâneo das cargas positivas, devido a uma espécie de ‘efeito de ponta’, a ionização tende a se acumular perto das elevações topográficas locais – exatamente onde estavam localizadas as câmeras. Nossa hipótese foi que, para se livrar dos sintomas indesejáveis da síndrome da serotonina, os animais fugiram para áreas mais baixas, onde a ionização não é tão expressiva”, explicou Raulin.

“Acreditamos que ambas as anomalias surgiram a partir de uma única causa: a atividade sísmica causando estresse na crosta terrestre e levando, entre outras coisas, à enorme ionização na interface solo-ar. Esperamos que nosso trabalho possa estimular ainda mais a investigação na área, que tem o potencial de auxiliar as previsões de curto prazo de riscos sísmicos”, declarou Rachel Grant, principal autora do artigo.

Independentemente da observação do comportamento animal, os resultados obtidos mostram que a previsão de terremotos poderia ser feita também mediante a detecção da ionização do ar, com o monitoramento do campo elétrico atmosférico. “Já temos detectores instalados no Brasil, no Peru e na Argentina. E pretendemos, em breve, instalar sensores de campo elétrico atmosférico nos lugares propícios a atividades sísmicas importantes. Isso daria uma previsibilidade da ordem de duas semanas ou até mais. Por ocasião do terremoto do Haiti, em janeiro de 2010, a rede SAVNET já tinha detectado flutuações na ionosfera com 12 dias de antecedência, com resultados publicados na revista NHESS – Natural Hazards and Earth System Sciences”, afirmou Raulin.

Brasil registra um grande terremoto a cada 50 anos (O Globo)

Cálculo é de novo centro de pesquisa, que vai detectar tremores em 80 pontos do país

Quatro instituições unem-se esta sexta-feira para formar o Serviço Sismológico Nacional. Os centros de pesquisa calculam que o país registra um terremoto de magnitude maior do que 6 graus na escala Richter a cada 50 anos, aproximadamente — o último foi em 1955, no noroeste de Mato Grosso, com índice de 6,2 graus. O tremor foi sentido em Cuiabá, a 370 km de distância.

As universidades de São Paulo (USP), de Brasília (UnB) e a Federal do Rio Grande do Norte (UFRN) trabalharão sob a coordenação do Observatório Nacional. O grupo mantém cerca de 80 estações sismológicas no país e registros iniciados em 1767. A mais recente foi inaugurada no mês passado, na Ilha de Trindade, a cerca de 1,2 mil quilômetros ao leste de Vitória, no Espírito Santo.

Leia mais sobre esse assunto em http://oglobo.globo.com/sociedade/ciencia/brasil-registra-um-grande-terremoto-cada-50-anos-14681727#ixzz3KMSImin8

(Renato Grandelle / O Globo)

How Big Could a Man-Made Earthquake Get? (Popular Mechanics)

Scientists have found evidence that wastewater injection induced a record-setting quake in Oklahoma two years ago. How big can a man-made earthquake get, and will we see more of them in the future?

By Sarah Fecht – April 2, 2013 5:00 PM

hydraulic fracking drilling illustration

Hydraulic fracking drilling illustration. Brandon Laufenberg/Getty Images

In November 2011, a magnitude-5.7 earthquake rattled Prague, Okla., and 16 other nearby states. It flattened 14 homes and many other buildings, injured two people, and set the record as the state’s largest recorded earthquake. And according to a new study in the journal Geology, the event can also claim the title of Largest Earthquake That’s Ever Been Induced by Fluid Injection.”

In the paper, a team of geologists pinpoints the quake’s starting point at less than 200 meters (about 650 feet) from an injection well where wastewater from oil drilling was being pumped into the ground at high pressures. At 5.7 magnitude, the Prague earthquake was about 10 times stronger than the previous record holder: a magnitude-4.8 Rocky Mountain Arsenal earthquake in Colorado in 1967, caused by the U.S. Army injecting a deep well with 148,000 gallons per day of fluid wastes from chemical-weapons testing. So how big can these man-made earthquakes get?

The short answer is that scientists don’t really know yet, but it’s possible that fluid injection could cause some big ones on very rare occasions. “We don’t see any reason that there should be any upper limit for an earthquake that is induced,” says Bill Ellsworth, a geophysicist with the U.S. Geological Survey, who wasn’t involved in the new study.

As with natural earthquakes, most man-made earthquakes have been small to moderate in size, and most are felt only by seismometers. Larger quakes are orders of magnitude rarer than small quakes. For example, for every 1000 magnitude-1.0 earthquakes that occur, expect to see 100 magnitude-2.0s, 10 magnitude-3.0s, just 1 magnitude-4.0, and so on. And just as with natural earthquakes, the strength of the induced earthquake depends on the size of the nearby fault and the amount of stress acting on it. Some faults just don’t have the capacity to cause big earthquakes, whether natural or induced.

How do Humans Trigger Earthquakes?

Faults have two major kinds of stressors: shear stress, which makes two plates slide past each other along the fault line, and normal stress, which pushes the two plates together. Usually the normal stress keeps the fault from moving sideways. But when a fluid is injected into the ground, as in Prague, that can reduce the normal stress and make it easier for the fault to slip sideways. It’s as if if you have a tall stack of books on a table, Ellsworth says: If you take half the books away, it’s easier to slide the stack across the table.

“Water increases the fluid pressure in pores of rocks, which acts against the pressure across the fault,” says Geoffrey Abers, a Columbia University geologist and one of the new study’s authors. “By increasing the fluid pressure, you’re decreasing the strength of the fault.”

A similar mechanism may be behind earthquakes induced by large water reservoirs. In those instances, the artificial lake behind a dam causes water to seep into the pore spaces in the ground. In 1967, India’s Koyna Dam caused a 6.5 earthquake that killed 177 people, injured more than 2000, and left 50,000 homeless. Unprecedented seasonal fluctuations in water level behind a dam in Oroville, Calif., are believed to be behind the magnitude-6.1 earthquake that occurred there in 1975.

Extracting a fluid from the ground can also contribute to triggering a quake. “Think about filling a balloon with water and burying it at the beach,” Ellsworth says. “If you let the water out, the sand will collapse inward.” Similarly, when humans remove large amounts of oil and natural gas from the ground, it can put additional stress on a fault line. “In this case it may be the shear stresses that are being increased, rather than normal stresses,” Ellsworth says.

Take the example of the Gazli gas field in Uzbekistan, thought to be located in a seismically inactive area when drilling began in 1962. As drillers removed the natural gas, the pressure in the gas field dropped from 1030 psi in 1962 to 515 psi in 1976, then down to 218 psi in 1985. Meanwhile, three large magnitude-7.0 earthquakes struck: two in 1976 and one in 1984. Each quake had an epicenter within 12 miles of Gazli and caused a surface uplift of some 31 inches. Because the quakes occurred in Soviet-era Uzbekistan, information about the exact locations, magnitudes, and causes are not available. However, a report by the National Research Council concludes that “observations of crustal uplift and the proximity of these large earthquakes to the Gazli gas field in a previously seismically quiet region strongly suggest that they were induced by hydrocarbon extraction.” Extraction of oil is believed to have caused at least three big earthquakes in California, with magnitudes of 5.9, 6.1, and 6.5.

Some people worry that hydraulic fracturing, or fracking‚Äîwherein high-pressure fluids are used to crack through rock layers to extract oil and natural gas‚Äîwill lead to an increased risk of earthquakes. However, the National Research Council report points out that there are tens of thousands of hydrofracking wells in existence today, and there has only been one case in which a “felt” tremor was linked to fracking. That was a 2.3 earthquake in Blackpool, England, in 2011, which didn’t cause any significant damage. Although scientists have known since the 1920s that humans trigger earthquakes, experts caution that it’s not always easy to determine whether a specific event was induced.

Are Human Activities Making Quakes More Common?

Human activities have been linked to increased earthquake frequencies in certain areas. For instance, researchers have shown a strong correlation between the volume of fluid injected into the Rocky Mountain Arsenal well and the frequency of earthquakes in that area.

Geothermal-energy sites can also induce many earthquakes, possibly due to pressure, heat, and volume changes. The Geysers in California is the largest geothermal field in the U.S., generating 725 megawatts of electricity using steam from deep within the earth. Before The Geysers began operating in 1960, seismic activity was low in the area. Now the area experiences hundreds of earthquakes per year. Researchers have found correlations between the volume of steam production and the number of earthquakes in the region. In addition, as the area of the steam wells increased over the years, so did the spatial distribution of earthquakes.

Whether or not human activity is increasing the magnitude of earthquakes, however, is more of a gray area. When it comes to injection wells, evidence suggests that earthquake magnitudes rise along with the volume of injected wastewater, and possibly injection pressure and rate of injection as well, according to a statement from the Department of Interior.

The vast majority of earthquakes caused by The Geysers are considered to be microseismic events—too small for humans to feel. However, researchers from Lawrence Berkeley National Laboratory note that magnitude-4.0 earthquakes, which can cause minor damage, seem to be increasing in frequency.

The new study says that though earthquakes with a magnitude of 5.0 or greater are rare east of the Rockies, scientists have observed an 11-fold increase between 2008 and 2011, compared with 1976 through 2007. But the increase hasn’t been tied to human activity. “We do not really know what is causing this increase, but it is remarkable,” Abers says. “It is reasonable that at least some may be natural.”

Scientists Underestimated Potential for Tohoku Earthquake: Now What? (Science Daily)

Jan. 23, 2013 — The massive Tohoku, Japan, earthquake in 2011 and Sumatra-Andaman superquake in 2004 stunned scientists because neither region was thought to be capable of producing a megathrust earthquake with a magnitude exceeding 8.4.

Seismograph. (Credit: © huebi71 / Fotolia)

Now earthquake scientists are going back to the proverbial drawing board and admitting that existing predictive models looking at maximum earthquake size are no longer valid.

In a new analysis published in the journal Seismological Research Letters, a team of scientists led by Oregon State University’s Chris Goldfinger describes how past global estimates of earthquake potential were constrained by short historical records and even shorter instrumental records. To gain a better appreciation for earthquake potential, he says, scientists need to investigate longer paleoseismic records.

“Once you start examining the paleoseismic and geodetic records, it becomes apparent that there had been the kind of long-term plate deformation required by a giant earthquake such as the one that struck Japan in 2011,” Goldfinger said. “Paleoseismic work has confirmed several likely predecessors to Tohoku, at about 1,000-year intervals.”

The researchers also identified long-term “supercycles” of energy within plate boundary faults, which appear to store this energy like a battery for many thousands of years before yielding a giant earthquake and releasing the pressure. At the same time, smaller earthquakes occur that do not to any great extent dissipate the energy stored within the plates.

The newly published analysis acknowledges that scientists historically may have underestimated the number of regions capable of producing major earthquakes on a scale of Tohoku.

“Since the 1970s, scientists have divided the world into plate boundaries that can generate 9.0 earthquakes versus those that cannot,” said Goldfinger, a professor in OSU’s College of Earth, Ocean, and Atmospheric Sciences. “Those models were already being called into question when Sumatra drove one stake through their heart, and Tohoku drove the second one.

“Now we have no models that work,” he added, “and we may not have for decades. We have to assume, however, that the potential for 9.0 subduction zone earthquakes is much more widespread than originally thought.”

Both Tohoku and Sumatra were written off in the textbooks as not having the potential for a major earthquake, Goldfinger pointed out.

“Their plate age was too old, and they didn’t have a really large earthquake in their recent history,” Goldfinger said. “In fact, if you look at a northern Japan seismic risk map from several years ago, it looks quite benign — but this was an artifact of recent statistics.”

Paleoseismic evidence of subduction zone earthquakes is not yet plentiful in most cases, so little is known about the long-term earthquake potential of most major faults. Scientists can determine whether a fault has ruptured in the past — when and to what extent — but they cannot easily estimate how big a specific earthquake might have been. Most, Goldfinger says, fall into ranges — say, 8.4 to 8.7.

Nevertheless, that type of evidence can be more telling than historical records because it may take many thousands of years to capture the full range of earthquake behavior.

In their analysis, the researchers point to several subduction zone areas that previously had been discounted as potential 9.0 earthquake producers — but may be due for reconsideration. These include central Chile, Peru, New Zealand, the Kuriles fault between Japan and Russia, the western Aleutian Islands, the Philippines, Java, the Antilles Islands and Makran, Pakistan/Iran.

Onshore faults such as the Himalayan Front may also be hiding outsized earthquakes, the researchers add. Their work was supported by the National Science Foundation.

Goldfinger, who directs the Active Tectonics and Seafloor Mapping Laboratory at Oregon State, is a leading expert on the Cascadia Subduction Zone off the Pacific Northwest coast of North America. His comparative studies have taken him to the Indian Ocean, Japan and Chile, and in 2007, he led the first American research ship into Sumatra waters in nearly 30 years to study similarities between the Indian Ocean subduction zone and Cascadia.

Paleoseismic evidence abounds in the Cascadia Subduction Zone, Goldfinger pointed out. When a major offshore earthquake occurs, the disturbance causes mud and sand to begin streaming down the continental margins and into the undersea canyons. Coarse sediments called turbidites run out onto the abyssal plain; these sediments stand out distinctly from the fine particulate matter that accumulates on a regular basis between major tectonic events.

By dating the fine particles through carbon-14 analysis and other methods, Goldfinger and colleagues can estimate with a great deal of accuracy when major earthquakes have occurred. Over the past 10,000 years, there have been 19 earthquakes that extended along most of the Cascadia Subduction Zone margin, stretching from southern Vancouver Island to the Oregon-California border.

“These would typically be of a magnitude from about 8.7 to 9.2 — really huge earthquakes,” Goldfinger said. “We’ve also determined that there have been 22 additional earthquakes that involved just the southern end of the fault. We are assuming that these are slightly smaller — more like 8.0 — but not necessarily. They were still very large earthquakes that if they happened today could have a devastating impact.”

Other researchers on the analysis include Yasutaka Ikeda of University of Tokyo, Robert S. Yeats of Oregon State University, and Junjie Ren, of the Chinese Seismological Bureau.

Journal Reference:

  1. C. Goldfinger, Y. Ikeda, R. S. Yeats, J. Ren. Superquakes and SupercyclesSeismological Research Letters, 2013; 84 (1): 24 DOI: 10.1785/0220110135

How animals predict earthquakes (BBC)

1 December 2011

By Victoria Gill – Science reporter, BBC Nature

Common toadCan pond-dwelling animals pick up pre-earthquake signals?

Animals may sense chemical changes in groundwater that occur when an earthquake is about to strike.

This, scientists say, could be the cause of bizarre earthquake-associated animal behaviour.

Researchers began to investigate these chemical effects after seeing a colony of toads abandon its pond in L’Aquila, Italy, in 2009 – days before a quake.

They suggest that animal behaviour could be incorporated into earthquake forecasting.

When you think of all of the many things that are happening to these rocks, it would be weird if the animals weren’t affected in some way” – Rachel GrantThe Open University

The team’s findings are published in the International Journal of Environmental Research and Public Health. In this paper, they describe a mechanism whereby stressed rocks in the Earth’s crust release charged particles that react with the groundwater.

Animals that live in or near groundwater are highly sensitive to any changes in its chemistry, so they might sense this days before the rocks finally “slip” and cause a quake.

The team, led by Friedemann Freund from Nasa and Rachel Grant from the UK’s Open University hope their hypothesis will inspire biologists and geologists to work together, to find out exactly how animals might help us recognise some of the elusive signs of an imminent earthquake.

Strange behaviour

The L’Aquila toads are not the first example of strange animal behaviour before a major seismic event. There have been reports throughout history of reptiles, amphibians and fish behaving in unusual ways just before an earthquake struck.

STRANGE OR NOT

  • In July 2009, just hours after a large earthquake in San Diego, local residents discovered dozens of Humboldt squid washed up on beaches. These deep sea squid are usually found at depths of between 200 and 600m
  • At 5.58am on 28 June 1992 the ground began to shake in the Mojave Desert, California, right in the middle of a scientific study on desert harvester ants. Measurements revealed the ants did not change their behaviour at all during the earthquake, the largest to strike the US in four decades.

In 1975, in Haicheng, China, for example, many people spotted snakes emerging from their burrows a month before the city was hit by a large earthquake.

This was particularly odd, because it occurred during the winter. The snakes were in the middle of their annual hibernation, and with temperatures well below freezing, venturing outside was suicide for the cold-blooded reptiles.

But each of these cases – of waking reptiles, fleeing amphibians or deep-sea fish rising to the surface – has been an individual anecdote. And major earthquakes are so rare that the events surrounding them are almost impossible to study in detail.

This is where the case of the L’Aquila toads was different.

Toad exodus

Ms Grant, a biologist from the Open University, was monitoring the toad colony as part of her PhD project.

“It was very dramatic,” she recalled. “It went from 96 toads to almost zero over three days.”

Ms Grant published her observations in the Journal of Zoology.

“After that, I was contacted by Nasa,” she told BBC Nature.

Scientists at the US space agency had been studying the chemical changes that occur when rocks are under extreme stress. They wondered if these changes were linked to the mass exodus of the toads.

Their laboratory-based tests have now revealed, not only that these changes could be connected, but that the Earth’s crust could directly affect the chemistry of the pond that the toads were living and breeding in at the time.

Toads mating (c) Rachel GrantAll of the toads left the breeding colony days before the 2009 earthquake

Nasa geophysicist Friedemann Freund showed that, when rocks were under very high levels of stress – for example by the “gargantuan tectonic forces” just before an earthquake, they release charged particles.

These charged particles can flow out into the surrounding rocks, explained Dr Freund. And when they arrive at the Earth’s surface they react with the air – converting air molecules into charged particles known as ions.

“Positive airborne ions are known in the medical community to cause headaches and nausea in humans and to increase the level of serotonin, a stress hormone, in the blood of animals,” said Dr Freund. They can also react with water, turning it into hydrogen peroxide.

This chemical chain of events could affect the organic material dissolved in the pond water – turning harmless organic material into substances that are toxic to aquatic animals.

It’s a complicated mechanism and the scientists stress that it needs to be tested thoroughly.

But, Dr Grant says this is the first convincing possible mechanism for a “pre-earthquake cue” that aquatic, semi-aquatic and burrowing animals might be able to sense and respond to.

“When you think of all of the many things that are happening to these rocks, it would be weird if the animals weren’t affected in some way,” she said.

Dr Freund said that the behaviour of animals could be one of a number of connected events that might forecast an earthquake.

“Once we understand how all of these signals are connected,” he told BBC Nature, “if we see four of five signals all pointing in [the same] direction, we can say, ‘ok, something is about to happen’.”

*   *   *

Toads can ‘predict earthquakes’ and seismic activity

Wednesday, 31 March 2010

By Matt Walker 
Editor, Earth News

Common toad (Bufo bufo)

Common toads sense danger

Common toads appear to be able to sense an impending earthquake and will flee their colony days before the seismic activity strikes.

The evidence comes from a population of toads which left their breeding colony three days before an earthquake that struck L’Aquila in Italy in 2009.

How toads sensed the quake is unclear, but most breeding pairs and males fled.

They reacted despite the colony being 74km from the quake’s epicentre, say biologists in the Journal of Zoology.

It is hard to objectively and quantifiably study how animals respond to seismic activity, in part because earthquakes are rare and unpredictable.

Some studies have been done on how domestic animals respond, but measuring the response of wild animals is more difficult.

Even those that have been shown to react, such as fish, rodents and snakes tend to do so shortly before an earthquakes strikes, rather than days ahead of the event.

However, biologist Dr Rachel Grant of the Open University, in Milton Keynes, UK, was routinely studying the behaviour of various colonies of common toads on a daily basis in Italy around the time a massive earthquake struck.

Her studies included a 29-day period gathering data before, during and after the earthquake that hit Italy on 6 April 2009.

The quake, a 6.3-magnitude event, struck close to L’Aquila city, about 95km (60 miles) north-east of Rome.

Dr Grant was studying toads 74km away in San Ruffino Lake in central Italy, when she recorded the toads behaving oddly.

Five days before the earthquake, the number of male common toads in the breeding colony fell by 96%.

Common frogs (Rana temporaria) mating

That is highly unusual for male toads: once they have bred, they normally remain active in large numbers at breeding sites until spawning has finished.

Yet spawning had barely begun at the San Ruffino Lake site before the earthquake struck.

Also, no weather event could be linked to the toads’ disappearance.

Three days before the earthquake, the number of breeding pairs also suddenly dropped to zero.

While spawn was found at the site up to six days before the earthquake, and again six days after it, no spawn was laid during the so-called earthquake period – the time from the first main shock to the last aftershock.

“Our study is one of the first to document animal behaviour before, during and after an earthquake,” says Dr Grant.

She believes the toads fled to higher ground, possibly where they would be at less risk from rock falls, landslides and flooding.

Sensing danger

Exactly how the toads sense impending seismic activity is unclear.

The shift in the toads’ behaviour coincided with disruptions in the ionosphere, the uppermost electromagnetic layer of the earth’s atmosphere, which researchers detected around the time of the L’Aquila quake using a technique known as very low frequency (VLF) radio sounding.

Such changes to the atmosphere have in turn been linked by some scientists to the release of radon gas, or gravity waves, prior to an earthquake.

In the case of the L’Aquila quake, Dr Grant could not determine what caused the disruptions in the ionosphere.

However, her findings do suggest that the toads can detect something.

“Our findings suggest that toads are able to detect pre-seismic cues such as the release of gases and charged particles, and use these as a form of earthquake early warning system,” she says.

Ants ignore quakes

One other study has quantified an animal’s response to a major earthquake.

Researchers had the serendipitous opportunity to measure how the behaviour of the desert harvester ant (Messor pergandei) changed as the ground began to tremble in the Mojave Desert, California, on 28 June 1992.

The largest quake to hit the US in four decades struck during the middle of an ongoing study, which measured how many ants walked the trails to and from the colony, the distributions of worker ants and even how much carbon dioxide the ants produced.

However, in response to that 7.4 magnitude quake, the ants did not appear to alter their behaviour at all.

ITALIAN EARTHQUAKE

 

Itália condena sete cientistas por não prever terremoto (Folha de São Paulo)

JC e-mail 4609, de 23 de Outubro de 2012.

Em 2009, o abalo sísmico em L’Aquila matou mais de 300 pessoas e deixou cerca de 65 mil desabrigadas. Justiça alega que os especialistas foram negligentes.

Um tribunal da Itália condenou ontem (22) sete cientistas a cumprir seis anos de prisão por não terem previsto o terremoto que atingiu o país em 2009, na cidade de L’Aquila, região de Abruzzo. Mais de 300 pessoas morreram.

Todos os cientistas, que vão recorrer em liberdade, eram membros da Comissão Nacional para Previsão e Prevenção de Riscos. Foram acusados de negligência, por não terem analisado corretamente as possibilidades do terremoto acontecer e, assim, alertar as autoridades.

Entre os sete condenados estão grandes nomes da ciência italiana, como o professor Enzo Boschi, que presidiu o Instituto Nacional de Geofísica e Vulcanologia, e o vice-diretor da Defesa Civil, Bernardo de Bernardinis.

Cientistas de diversas partes do mundo protestaram contra a decisão do tribunal em condená-los por homicídio culposo (quando não há intenção de matar). Em protesto, uma carta com mais de 5.000 assinaturas de cientistas foi entregue ao presidente italiano, Giorgio Napolitano, alegando que a ciência não possui meios para prever terremotos, e que o processo pode impedir que futuramente especialistas aconselhem governos a respeito de riscos sísmicos.

Imprevisível – Segundo a técnica de sismologia do Instituto de Astronomia, Geofísica e Ciências Atmosféricas da USP (IAG-USP) Célia Fernandes, é muito difícil identificar o momento exato em que irá acontecer um abalo sísmico. “Todos os profissionais de sismologia trabalham com o objetivo de prever terremotos, mas não existe regra na natureza. Mesmo a recorrência de sismos não é garantia de que um terremoto de grande magnitude está prestes a acontecer”, afirma.

Os cientistas se reuniram na cidade de L’Aquila em 31 de março de 2009, seis dias antes do terremoto, e não comunicaram sobre a chance de um abalo sísmico. Para o tribunal, eles falharam por terem subestimado os riscos, limitando a ação das autoridades públicas, que não tiveram tempo suficiente para tomar medidas necessárias para proteger a população.

Segundo os promotores, uma série de tremores de baixo nível atingiu a região nos meses que antecederam o terremoto e isso deveria ter sido interpretado pelos especialistas como um sinal do que estava para acontecer.

O terremoto de magnitude 6,3 graus atingiu L’Aquila em abril de 2009. Além das mortes, também feriu outras 1.500 pessoas. Estima-se que 65 mil tenham ficado desabrigadas. A condenação dos cientistas ainda não é definitiva. Eles devem entrar com um recurso.

*   *   *

Artigos:

David Alexander. An evaluation of medium-term recovery processes after the 6 April 2009 earthquake in L’Aquila, Central Italy. Environmental Hazards, iFirst.

Abstract

This article uses the earthquake of 6 April 2009 at L’Aquila, central Italy (magnitude 6.3) as a case history of processes of recovery from disaster. These are evaluated according to criteria linked to both vulnerability analysis and disaster risk-reduction processes. The short- and medium-term responses to the disaster are evaluated, and 11 criticisms are made of the Italian Government’s policy on transitional shelter, which has led to isolation, social fragmentation and deprivation of services. Government policy on disaster risk is further evaluated in the light of the UNISDR Hyogo Framework for Action. Lack of governance and democratic participation is evident in the response to disasters. It is concluded that without an adequately planned strategy for managing the long-term recovery process, events such as the L’Aquila earthquake open up Pandora’s box of unwelcome consequences, including economic stagnation, stalled reconstruction, alienation of the local population, fiscal deprivation and corruption. Such phenomena tend to perpetuate rather than reduce vulnerability to disasters.

“[…] science and scientists were not on trial. The hypothesis of culpability being tested in the courts referred to the failure to adopt a precautionary approach in the face of clear indications of impending seismic impact, not failure to predict an earthquake, and this is amply documented in official records”.

David E. Alexander. The L’Aquila Earthquake of 6 April 2009 and Italian Government Policy on Disaster Response. Journal of Natural Resources Policy Research, Vol. 2, Iss. 4, 2010

Abstract

This paper describes the impact of the earthquake that struck the central Italian city of L’Aquila on 6 April 2009, killing 308 people and leaving 67 500 homeless. The pre-impact, emergency, and early recovery phases are discussed in terms of the nature and effectiveness of government policy. Disaster risk reduction (DRR) in Italy is evaluated in relation to the structure of civil protection and changes wrought by both the L’Aquila disaster and public scandals connected with the misappropriation of funds. Six of the most important lessons are derived from this analysis and related to DRR needs both in Italy and elsewhere in the world.

“As articulated at the meeting of the Commission on Major Risks on 31 March 2009, the Italian Government’s position was unequivocal: there was no cause for alarm. This attitude permeated its way down the ranks of the civil protection system. Then, at 00:30 hrs on Monday 6 April 2010, a tremor that was larger than usual shook L’Aquila. Residents rushed out of their houses in alarm. The strategy adopted by civil protection authorities was to tour the streets with loudspeakers advising people to calm down and return home. In the town of Pagánica, less than 10 km northeast of L’Aquila, residents did exactly that: in the ensuing main shock three hours later, eight of them died and 40 were seriously injured. In L’Aquila city I investigated one case in which a young lady had decided to remain out of doors after the foreshock, while her parents returned home. Their bodies were recovered by firemen from a space barely 15 cm wide into which the building had compressed as it collapsed”.

Earthquake Hazards Map Study Finds Deadly Flaws (Science Daily)

ScienceDaily (Aug. 31, 2012) — Three of the largest and deadliest earthquakes in recent history occurred where earthquake hazard maps didn’t predict massive quakes. A University of Missouri scientist and his colleagues recently studied the reasons for the maps’ failure to forecast these quakes. They also explored ways to improve the maps. Developing better hazard maps and alerting people to their limitations could potentially save lives and money in areas such as the New Madrid, Missouri fault zone.

“Forecasting earthquakes involves many uncertainties, so we should inform the public of these uncertainties,” said Mian Liu, of MU’s department of geological sciences. “The public is accustomed to the uncertainties of weather forecasting, but foreseeing where and when earthquakes may strike is far more difficult. Too much reliance on earthquake hazard maps can have serious consequences. Two suggestions may improve this situation. First, we recommend a better communication of the uncertainties, which would allow citizens to make more informed decisions about how to best use their resources. Second, seismic hazard maps must be empirically tested to find out how reliable they are and thus improve them.”

Liu and his colleagues suggest testing maps against what is called a null hypothesis, the possibility that the likelihood of an earthquake in a given area — like Japan — is uniform. Testing would show which mapping approaches were better at forecasting earthquakes and subsequently improve the maps.

Liu and his colleagues at Northwestern University and the University of Tokyo detailed how hazard maps had failed in three major quakes that struck within a decade of each other. The researchers interpreted the shortcomings of hazard maps as the result of bad assumptions, bad data, bad physics and bad luck.

Wenchuan, China — In 2008, a quake struck China’s Sichuan Province and cost more than 69,000 lives. Locals blamed the government and contractors for not making buildings in the area earthquake-proof, according to Liu, who says that hazard maps bear some of the blame as well since the maps, based on bad assumptions, had designated the zone as an area of relatively low earthquake hazard.

Léogâne, Haiti — The 2010 earthquake that devastated Port-au-Prince and killed an estimated 316,000 people occurred along a fault that had not caused a major quake in hundreds of years. Using only the short history of earthquakes since seismometers were invented approximately one hundred years ago yielded hazard maps that were didn’t indicate the danger there.

Tōhoku, Japan — Scientists previously thought the faults off the northeast coast of Japan weren’t capable of causing massive quakes and thus giant tsunamis like the one that destroyed the Fukushima nuclear reactor. This bad understanding of particular faults’ capabilities led to a lack of adequate preparation. The area had been prepared for smaller quakes and the resulting tsunamis, but the Tōhoku quake overwhelmed the defenses.

“If we limit our attention to the earthquake records in the past, we will be unprepared for the future,” Liu said. “Hazard maps tend to underestimate the likelihood of quakes in areas where they haven’t occurred previously. In most places, including the central and eastern U.S., seismologists don’t have a long enough record of earthquake history to make predictions based on historical patterns. Although bad luck can mean that quakes occur in places with a genuinely low probability, what we see are too many ‘black swans,’ or too many exceptions to the presumed patterns.”

“We’re playing a complicated game against nature,” said the study’s first author, Seth Stein of Northwestern University. “It’s a very high stakes game. We don’t really understand all the rules very well. As a result, our ability to assess earthquake hazards often isn’t very good, and the policies that we make to mitigate earthquake hazards sometimes aren’t well thought out. For example, the billions of dollars the Japanese spent on tsunami defenses were largely wasted.

“We need to very carefully try to formulate the best strategies we can, given the limits of our knowledge,” Stein said. “Understanding the uncertainties in earthquake hazard maps, testing them, and improving them is important if we want to do better than we’ve done so far.”

The study, “Why earthquake hazard maps often fail and what to do about it,” was published by the journal Tectonophysics. First author of the study was Seth Stein of Northwestern University. Robert Geller of the University of Tokyo was co-author. Mian Liu is William H. Byler Distinguished Chair in Geological Sciences in the College of Arts and Science at the University of Missouri.