ALBERT

Description: Much debate within the weather, climate, disaster mitigation, and insurance communities centers on whether rising sea-surface temperatures in the North Atlantic Ocean due to anthropogenic global warming are resulting in discernible trends in hurricane frequency or energy. However, some of the apparent increase in hurricane frequency may be due to the recent availability of aircraft- and satellite-based observations. A possible approach to this issue is via microseisms, seismic signals traditionally thought of as noise because they are not generated by earthquakes. These surface waves generated by ocean storms are detected even in continental interiors far from source regions. Here we show that the August 1992 Saffir/Simpson category 5 Hurricane Andrew can be detected using microseisms recorded at the Harvard, Massachusetts, seismic station even while the storm is as far as [~]2000 km away and still at sea. When applied to decades of existing analog seismograms, this methodology could yield a seismically identified hurricane record for comparison to the pre-aircraft and pre-satellite observational record.

Description: During World War II, future Nobel Prize winner Kenneth Arrow served as a military weather forecaster. "My colleagues had the responsibility of preparing long-range weather forecasts, i.e., for the following month," he wrote. "The statisticians among us subjected these forecasts to verification and found they differed in no way from chance. The forecasters themselves were convinced and requested that the forecasts be discontinued. The reply read approximately like this: `The commanding general is well aware that the forecasts are no good. However, he needs them for planning purposes.'" (Gardner 2010). Seismologists often encounter a similar situation when developing earthquake hazard maps, which ideally describe the level of earthquake hazards in a region and provide a scientific foundation for earthquake preparation and mitigation. However, in recent years many large and destructive earthquakes have occurred in places mapped as having relatively low hazard (Kerr 2011). A striking example is the March 2011 M 9.1 earthquake off Tohoku, Japan, which occurred in an area shown by the Japanese national earthquake hazard map as one of relatively low hazard. Figure 1, from Geller (2011), illustrates his point that ...in recent years many large and destructive earthquakes have occurred in places mapped as having relatively low hazard... The regions assessed as most dangerous are the zones of three hypothetical "scenario earthquakes" (Tokai, Tonankai, and Nankai; see map). However, since 1979, earthquakes that caused 10 or more fatalities in Japan actually occurred in places assigned a relatively low probability. This discrepancy—the latest in a string of negative results for the characteristic earthquake model and its cousin, the seismic-gap model—strongly suggests that the hazard map and the methods used to produce it are flawed and should be discarded. Similar discrepancies have occurred around the world. The 2008 Wenchuan earthquake...

Description: We present a comprehensive study of the Earth’s gravest spheroidal modes excited by the Maule, Chile, earthquake of 27 February 2010, using uninterrupted time series extending over a minimum of 19 and a maximum of 93 days. For each of 101 station–mode combinations, we use the formalism of Stein and Geller (1977) to compute the relative excitation of the 2l+1 singlets in the relevant geometry and obtain an estimate of the seismic moment by best fitting the observed spectrum to that of the resulting synthetic computed for the same recording window. The average results for seven spheroidal and two radial modes deviate no more than 12% from the Global Centroid Moment Tensor moment of 1.86×1029??dyn?·???cm, with no evident trend with frequency. In other words, we fail to document an ultralow-frequency component (expressed as an increase of moment with period) in the source of the 2010 event. This result indicates that such components are not universal features of megaquakes, even though they had been documented for the 1960 Chilean, 2004 Sumatran, and 1964 Alaskan events (the only three events with larger moments in the past 50 years). In this respect, the 2010 earthquake is most comparable to the slightly smaller 2005 Nias event, which incidentally also featured a bilateral rupture.