09/19/2018 - 3:30pm to 4:30pm
Munk Conference Room
Seismology in academia emphasizes the study of tectonics, Earth structure, and earthquake physics. But seismology is also an applied science—helping to quantify seismic hazard, and to estimate the strength of ground shaking that our infrastructure should handle; and to detect and interpret signals from explosions of different types and sizes.
Whether we are interested in pure or applied seismology, progress can come from radical and achievable improvements in how events are detected, located, identified, and sized.
The key agencies in charge of seismic monitoring still emphasize the analysis of events one-at-a-time.
I shall describe huge improvements in quantifying seismicity, mostly drawn from studies in mainland East Asia, that result from processing seismic waveforms of groups of events, often using empirical methods applied to messy phases that lack clear onsets and identifiable arrival times. Location precision using sparse regional networks is sometimes achievable at the level of a few tens of meters, rather than the several km errors typical for traditional bulletins. And then: modern methods of detecting and characterizing small seismic events, applied to North Korea, have revealed a lineation (extending about 700 m) of small aftershocks of the last nuclear test explosion. They appear to be explosion-induced earthquakes, occurring several km to the north of the huge explosion of September 3, 2017. (Work done with Won-Young Kim and David Schaff at Lamont, just accepted for publication in SRL.)
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