Far-field simulation of the 1946 Aleutian tsunami

We present hydrodynamic far-field simulations of the Aleutian tsunami of 1946 April 1, using both a dislocation source representing a slow earthquake and a dipolar one modelling a large landslide. The earthquake source is derived from the recent seismological study by López and Okal, while the landslide source was previously used to explain the exceptional run-up at Scotch Cap in the near field. The simulations are compared to a field data set previously compiled from testimonies of elderly witnesses at 27 far-field locations principally in the Austral and Marquesas Islands, with additional sites at Pitcairn, Easter and Juan Fernández. We find that the data set is modelled satisfactorily by the dislocation source, while the landslide fails to match the measured amplitudes, and to give a proper rendition of the physical interaction of the wavefield with the shore, in particular at Nuku Hiva, Marquesas. The emerging picture is that the event involved both a very slow earthquake, responsible for the far-field tsunami, and a major landslide explaining the near-field run-up, but with a negligible contribution in the far field.     

Determination of earthquake early warning parameters, τc and Pd, for southern California

We explore a practical approach to earthquake early warning in southern California by determining a ground-motion period parameter  τ _c   and a high-pass filtered displacement amplitude parameter Pd from the initial 3 s of the P waveforms recorded at the Southern California Seismic Network stations for earthquakes with M > 4.0. At a given site, we estimate the magnitude of an event from  τ _c   and the peak ground-motion velocity ( PGV ) from Pd . The incoming three-component signals are recursively converted to ground acceleration, velocity and displacement. The displacements are recursively filtered with a one-way Butterworth high-pass filter with a cut-off frequency of 0.075 Hz, and a P -wave trigger is constantly monitored. When a trigger occurs,  τ _c   and Pd are computed. We found the relationship between  τ _c   and magnitude ( M ) for southern California, and between Pd and PGV for both southern California and Taiwan. These two relationships can be used to detect the occurrence of a major earthquake and provide onsite warning in the area around the station where onset of strong ground motion is expected within seconds after the arrival of the P wave. When the station density is high, the methods can be applied to multistation data to increase the robustness of onsite early warning and to add the regional warning approach. In an ideal situation, such warnings would be available within 10 s of the origin time of a large earthquake whose subsequent ground motion may last for tens of seconds.     

上海市居民乡村旅游行为特征及感知研究

运用旅游心理学原理,采用比较分析和交互分析等研究方法,分析了上海市居民乡村旅游的人口学特征、行为偏好以及效果感知,并提出加强乡村旅游宣传力度、观念创新和服务管理等建议.