How Many Earthquakes Are There?

How Many Earthquakes Are There?

ScienceDaily (Oct. 8, 2008) — A new method for estimating the capability of a network to detect earthquakes suggests that the seismic monitoring network for Southern California, as an example, does not accurately reflect all earthquakes that register a magnitude of 3.3 or smaller within southern California, thereby giving seismologists an incomplete picture of recent and current seismicity.

The study, published in the October issue of the Bulletin of the Seismological Society of America, provides a new empirically-based approach for seismologists to understand the detection capabilities of seismic networks.

While today's improved seismic networks detect earthquakes down to low magnitudes in regions of the densest coverage, seismologists need to estimate the completeness magnitude which varies in space and time. This magnitude of completeness indicates the magnitude below which the earthquake catalog does not contain all events that occurred..

D. Schorlemmer of the University of Southern California (USC) and J. Woessner of the Swiss Seismological Service present a new approach to estimate the magnitude of completeness which will enable scientists to develop a richer understanding of the distribution of smaller earthquakes. The authors' new approach uses an analysis based on the actual performance of seismic stations rather than a theoretical assessment based on sampling of earthquakes.

This advancement is important because one way scientists estimate the number of large, damaging earthquakes is to study the distribution of small earthquakes. Without an accurate understanding of how likely the seismic networks are detecting earthquakes of different magnitudes, scientists may obtain incorrect seismic hazard estimates for an area.

WEATHER NOTE

Researchers study global warming impact on hurricanes

Florida Today

BREVARD COUNTY, Florida -- Federal researchers hope a supercomputer that crunches 76 trillion equations per second can shed light on whether global warming might lead to fewer, yet more powerful hurricanes.

The federal government has launched an intensive study of how global warming might impact hurricanes in coming decades.

The goal of the study is to better warn coastal communities, offshore Gulf of Mexico oil drilling operations, and other interests that could be affected by increased hurricane activity.

The National Center for Atmospheric Research (NCAR), will conduct the study, along with other federal agencies, universities, as well as the insurance and energy industries.

The Georgia Institute of Technology and several other universities are also collaborating on the research.

The project will use global climate and regional weather models, run on one of the world’s most powerful supercomputers. The models will examine future hurricane activity “in unprecedented detail,” according to a press release issued Wednesday by NCAR.

The study, which centers on the Gulf of Mexico and the Caribbean Sea, is part of a larger study of regional climate change between 1995 and 2055. Researchers will look at three decades in detail: 1995-2005, 2020-2030, and 2045-2055.

The simulations will run on NCAR’s flagship bluefire supercomputer. Manufactured by IBM, it is ranked as one of the 30 most powerful computers on Earth and can solve up to 76 trillion equations every second.

Researchers will analyze changes in hurricane frequency, intensity, and paths from now to the middle of the century. A major goal is to examine how several decades of greenhouse-gas buildup could affect regional climate and influence hurricanes and other critical weather patterns.

Preliminary results are expected early next year.

“It is clear from the impacts of recent hurricane activity that we urgently need to learn more about how hurricane intensity and behavior may respond to a warming climate,” NCAR scientist Greg Holland said in the release.

“The increasingly dense development along our coastlines and our dependence on oil from the Gulf of Mexico leave our society dangerously vulnerable to hurricanes,” said Holland, who is leading the project.

The new study follows reports by the U.S. Climate Change Science Program and Intergovernmental Panel on Climate Change, that found evidence for a link between global warming and hurricane activity.

MARITIME NOTE

Maritime Organization Seeks to Cut Air Pollution From Oceangoing Ships

By FELICITY BARRINGER

The International Maritime Organization on Thursday adopted stringent new controls on airborne pollution from the world’s 300,000 oceangoing vessels.

Emissions from ships steaming into ports from Rotterdam to Shanghai to Long Beach, are blamed for about 60,000 premature deaths around the world annually.

The new rules, which differ little from proposals the group approved in April, would cut the sulfur content of the fuels ships use in controlled areas along coasts by 63 percent as of July of 2010, and by more than 95 percent as of January 2015.

Oceangoing ships are largely propelled by bunker fuel, which is one of the most cost-effective — it provides more energy per gallon than the distilled products used in other diesel and gasoline engines — and environmentally destructive fuels in use anywhere.

Sulfur emissions are a major source of airborne fine particulates, which have been associated with pulmonary and cardiovascular disease. In some ports in Europe and in the United States, environmental groups, using the courts, and local governmental bodies have required ships to shut off their engines and plug in to the local electrical grid to keep ship operations functioning while in port.

The international group approved the measure with little discussion late Thursday at its meeting in London, according to Janea Scott, a lawyer with the Environmental Defense Fund who attended the meeting. Ms. Scott spoke by telephone from London.

Both shipping interests and environmental groups had been unsure if any major last-minute changes would be made, but with the exception of changes of a few months in two of the deadlines, the original proposals were approved.

Now individual countries must set the boundaries of the so-called emission control areas in which the new, stringent fuel standards apply. This sets the stage for a renewed tug of war as environmental advocates are likely to seek to include as much of a country’s offshore waters as possible in the emission control areas, while shipping interests are likely to call for far more limited boundaries.

Andreas Chrysostomou, the chairman of the Marine Environment Protection Committee, hailed the decision as “an historical moment,” Ms. Scott said.

T. L. Garrett, vice president of the Pacific Merchant Shipping Association, an industry trade group, said Thursday: “This is good news — we are fully supportive of this. We think the international approach that creates uniformity is the way to approach the issues.”

Ms. Scott of the Environmental Defense Fund said, “It’s really impressive when 168 nations can come together and agree on protective measures for the environment.” She added that the Environmental Protection Agency, which will propose the boundaries of the emission control areas, “should apply as soon as possible.”

In addition to setting limits for the offshore areas, the organization also cut the allowable standards for midocean operation. Currently, even though the average sulfur content of bunker fuel is about 27,000 parts per million, the rules allow fuel with up to 45,000 parts per million. This will be reduced to 35,000 parts per million in 2012 and to 5,000 parts per million in 2020, providing that a review demonstrates that there will be enough of the fuel available.

RS