World Agency of Planetary Monitoring & Earthquake Risk Reduction

The methods to detect the development of a large earthquake at an early time and to issue an appropriate warning have made great progress. Nevertheless, for population centers at risk, warnings can generally be issued only about 5–10 s before the strong shaking arrives. Systems and facilities that can benefit from a warning with such a short lead time include: Transportation systems, fire departments, medical facilities, schools, industrial plants, petroleum and gas pipelines, elevators, and power plants. However, for the population at home in vulnerable apartment buildings or at work in office buildings and factories that may not have been built following modern codes, the warning is too short for a person to reach a safe place. Although taking cover under a table can protect a person from falling objects, a structurally strong Earthquake Protection Unit (EPU) is required to save lives and limbs in a partially collapsing building. If a culture of earthquake awareness and the knowledge of early warning capabilities were developed, in which strong earthquakes closets could be bought in the lumber yard like tornado shelters, then the fine advances in earthquakes early warning could result in lives saved.KeywordsGround MotionEarly WarningStrong EarthquakeLarge EarthquakeHuman Development IndexThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

The earthquake catalog in southern Iceland between 20.25� W and 21.3� W is complete down to approximately Mw 0 and shows no evidence for mag- nitude shifts as a function of time since 1991. This means that 6902 earthquakes (M 0.1, depth 20 km) are available for studies of seismicity patterns preceding the two MS 6.6 mainshocks in 2000, in their source volumes and vicinity (20.25� W and 20.9� W). The power law of the frequency-magnitude relationship holds down to M0. Detailed mapping (including 3D mapping) of the b-value of the frequency- magnitude distribution shows that variations from b 0.6 to 1.4 exist over distances of about 2 km. This suggests that the tectonic fabric in southern Iceland is hetero- geneous on a small scale. The hypocenters of the two MS 6.6 mainshocks and one additional M 4.5 mainshock are associated with low b-values (0.6-0.8), statistically significantly different from volumes in their vicinity. Therefore, one can expect future mainshocks in southern Iceland to also emanate from volumes characterized by low b-values. However, the small dimensions of these asperities may render it difficult to identify them before the mainshocks occur. Low values of estimated local recur- rence times (500-2000 years) map the two fault zones that ruptured in 2000 against a background of local recurrence times longer than 5000 years. The first of the two M 6.6 mainshocks emanated from a volume of short estimated local recurrence time. This supports the hypothesis that asperities with short local recurrence times control locations of major ruptures. Mapping of b-values in cross sections shows anomalies of high b at the bottom of the seismogenic crust, correlating with the change of its thickness in the middle of the study area. These high b-value anomalies, and other pockets of such anomalies at shallower depths, are best interpreted as caused by high pore pressure because evidence of fluids under high pressure is ubiquitous in this area.

Quantitative estimates of potential losses that may be caused by future great earthquakes along the Himalaya suggest that as many as 150,000 people may die, 300,000 may be injured and typically 3,000 settlements will be affected in a single event. Scenario results used here vary and are based on ruptures of 150 km segments of the plate boundary at seven positions, where sufficient elastic energy is believed to be stored for magnitude eight earthquakes. The method of calculating these results was calibrated, using the 17 disastrous Indian earthquakes, which have occurred since 1980. About 50 settlements in the region are considered most at risk because in each more than 2000 fatalities may occur.