A food safety factory shutdown has Americans hunting for baby formula. Readying themselves for a covid-19 lockdown, Chinese in Beijing emptied store shelves. Emerging from lockdown, some in Shanghai are visiting well-provisioned markets. U.S.-China agricultural trade is booming, but many are still being left hungry. Food security, sustainability and safety remain issues.
Li, "Earthquake location problems in eastern Taiwan," 1995
USC thesis in Security.
August 26, 2009
Cheng-Ping Li, M.S.
Abstract (Summary)
The SMART 2 and HTN arrays of eastern Taiwan recorded 3-component digital data in 1991. Due to the synchronization problem, the conventional location method using the first P-arrival time can not be applied. Since the S-arrival can be picked considerable accuracy using digital 3-component data, we attempt to locate earthquakes by using Ts-Tp only.
We seek the best solution in the least squares sense through a non-linear optimization process. A location program is developed and tested based on S-P intervals and 3-D ray-tracing programs. Results showed that the accuracy of relocation strongly depends on the station distribution, model definition, and the accuracy of P- and S-picking. The hypocenters were consistently shifted from east to west, implying a lower velocity underneath the island of Taiwan. The particle motion is used to discriminate the contradicting relocation results from different data sets.
Advisor: Teng, Ta-Liang
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