Improving quake aftershock forecast
THE NEED to speed up work on a reliable system for predicting potential aftershocks in the days following a strong earthquake has become more urgent, say US scientists, after a rare quake earlier this year was found to have triggered many large, and potentially damaging, earthquakes around the world. Writing in Nature last month (26 September), researchers said that the magnitude 8.6 earthquake that struck off the coast of Sumatra, Indonesia, on 11 April this year unleashed an unprecedented number of large events as far away as Japan and Mexico. “The number of earthquakes worldwide of more than [magnitude 5.5] increased by a factor of five over a six-day period,” Roland Burgmann, a professor in the Department of Earth and Planetary Science at the University of California, United States, and one of the authors of the report, said. “No other recorded earthquake has triggered as many large aftershocks around the world. We believe this was because it was the largest ‘strike-slip’ earthquake (where the two sides of a fault slip horizontally past each other) ever recorded, involving horizontal motions. “Seismic waves from this type [of earthquake] are particularly strong and last long enough to affect distant fault zones,” he said. Last April’s quake followed 6–12 days of exceptionally low global seismicity, which — coupled with the strength and duration of the shaking related to the strike-slip geometry of the fault — may have been behind the large jump in global seismicity. John Vidale, a seismologist at the University of Washington, United States, said: “Prior work documented that earthquakes can trigger more earthquakes up to a certain size, up to a certain distance. But why should only small earthquakes get triggered… And why should there be a distance beyond which triggering doesn’t work? With just a single triggering ‘megaquake’, the conclusions will remain tentative until confirmed with follow-up studies, but our understanding of how earthquakes trigger one another has just gained a step up.” The strong and potentially damaging on-land shaking in Indonesia, Japan and Mexico caused by the Sumatra event has implications for the effect of a large earthquake on the global seismic hazard, the paper says. According to Burgmann, earthquakes triggered at much larger distances should be included in the definition of aftershocks if they occur immediately or just within a few days of a major earthquake.
Climate change mitigation ‘far cheaper than inaction’
TACKLING THE global climate crisis could reap significant economic benefits for both developed and developing countries, according to a new report. The impacts of climate change and a carbon-intensive economy cost the world around US$1.2 trillion a year — 1.6 per cent of the total global GDP (gross domestic product), states ‘Climate Vulnerability Monitor: A Guide to the Cold Calculus of A Hot Planet’. For this reason, “adapting to climate change is very likely a cost-effective investment in almost all cases and should be central to any climate change policy”, the report says. The new publication was launched during the 67th session of the UN General Assembly, in New York, United States, in September. It was produced by Development Assistance Research Associates (DARA), an independent aid analysis organisation, and the Climate Vulnerable Forum, a global partnership of nations that are disproportionately affected by global warming. The authors highlight that shifting the world economy to a low-carbon footing will cost around 0.5 per cent of GDP for the current decade. As the report points out, this is significantly lower than the actual and projected costs of responding to climate change and maintaining a carbon-intensive economy. The report warns that the impact of the expected increase in temperature and carbon-related pollution could double the actual costs to 3.2 per cent of GDP in 2030, and will cause six million deaths every year, up from 4.5 million each year. And although developing countries are the most vulnerable, “the world’s major economies are in no way spared”. “The US, China and India are expected to incur enormous losses that in 2030 for these three countries alone will collectively total US$2.5 trillion in economic costs and over 3 million deaths per year,” according to the report. Matthew McKinnon, head of DARA’s Climate Vulnerability Initiative team and the report’s lead author, said: “The conclusion contrasts with previous studies that generally justify expenses on climate action today, in relation to damages to be experienced much further down the line. Our estimated damages already far exceed the costs of action on climate change — costs that will only escalate rapidly if action on climate change is not urgently taken.” The report is a follow-up to the Climate Vulnerability Monitor 2010, which was released at the UN Climate Change conference, in Mexico in December 2010. Supported by high-level and technical panels, the 2012 report is “the most comprehensive ever” assessment of the impact of climate change, because it ranges from human health issues to economic sector pressures, extreme events and environmental concerns, McKinnon said.
“The monitor is unusual in particular for examining the current impact of climate change. Most climate change studies have much longer time horizons, such as 2050, 2100 or 2200,” he explained. José Antonio Milán Pérez, a climate change professor at the University of Commercial Science, Nicaragua, praised the report, saying that it represented “a significant scientific contribution for its comprehensiveness and extensive global and regional levels”. “The method extends the number of indicators, [to include] not only purely economic aspects, but also human aspects,” he added, and could act as a “reference for decision-makers”.