Hypocenter location of mixed events in real-time processing systems     

Vladimir Pinsky  Shigeki Horiuchi 《Journal of Seismology》2009,13(4):589-600

Automatic pickings in earthquake real-time monitoring systems often contain noise bursts and/or phases of different event(s) occurring almost simultaneously. Typically, a locator uses these picks as P and S waves arrival times coming from a single event and, therefore, should be complemented by a distinctive phase association logic. The method we propose manages to automatically associate data related to different events and eliminates the influence of spoiled data from single events. The method is based on “network beamforming”, a robust and stable algorithm, which utilizes a hypocenter grid search for the stack maximum of a set of complex exponents applied to the P phase readings. The algorithm separates the residual outliers and then uses them for location. If successful, a hypocenter is established for the interfering event. The solutions obtained are overall robust and independent from the estimate of origin times. The preliminary epicenter for the grid search is provided by the intersection of perpendicular bisectors in the modified “arrival order algorithm” or by the modified “T^now” algorithm, which uses non-arrival information. We applied this method to automatic first arrival phase readings of 915 events registered by the Hi-net Japan seismic network and our results are statistically promising. Here, we present two interesting and complicated examples.  相似文献   

Solar activity dependence of trans-equatorial ion whistler     

Shigeki Watanabe  Tadanori Ondoh 《Planetary and Space Science》1984,32(8):955-964

This paper describes occurrence probabilities and patterns of trans-equatorial proton (TEP), deuteron (TED) and helium (TEH) whistler from the ISIS-2 satellite in time compressed dynamic spectra. It is shown that the TEP whistlers have high occurrence probability in an active solar period, while the TED whistler has low occurrence probability. In a quiet solar period, the TEP whistler has a relatively lower occurrence probability than the TED whistler. The TEP whistler in a quiet solar period shows a strong seasonal variation. That is a higher occurrence probability in the winter than in the summer in the Northern Hemisphere. The curve of occurrence probability of the TED whistler has a valley (no occurrence) at the noon in a solar active period. The minimum occurrence probabilities, which depend on geomagnetic activity appear at about K_P = 4-5. These phenomena seem to be explained by using the bouncing surface diagram of multicomponent and inhomogeneous plasmas with various proton density. The spectral pattern of trans-equatorial ion whistlers and calculation of an approximate equation with regard to deuteron effect show that relative proton densities to electrons N_P/N_e decrease with increasing solar activity.  相似文献   

Australasian Tektites and Catastrophic Products Enclosed in Impact Ejecta Horizon from the Buntharik Impact Event in Thailand     

Sangad Bunopas  Paul Vella  Shigeki Hada  Henry Fontaine  Clive Burrett  Peter Haines  Somboon Khositanont  Kieren T. Howard 《Gondwana Research》2001,4(4):586

  相似文献   

Large-Scale Translation of Accreted Terranes Along Continental Margins     

Shigeki Hada  Mitsumasa Ito  C.A. Landis  P.A. Cawood 《Gondwana Research》2001,4(4):628-629

  相似文献   

Improved description of global mixed-layer depth using Argo profiling floats     

Shigeki Hosoda  Tsuyoshi Ohira  Kanako Sato  Toshio Suga 《Journal of Oceanography》2010,66(6):773-787

A global data set describing the gridded mixed-layer depth (MLD) in 10-day intervals was produced using high-quality Argo float data from 2001 to 2009. The characteristics and advantages provided by the new MLD data set are described here, including a comparison based on two different thresholds and using data sets of different vertical and temporal resolution. The MLD in the data set was estimated on the basis of a shallower depth of the iso-thermal layer (TLD) or iso-pycnal layer (PLD), calculated using the finite difference method. The MLD data are incorporated into 2° × 2° grid in the global ocean, including marginal seas. Also, two threshold values were used to examine differences in the MLD and its seasonal temporal variability. The characteristics and advantages of using the Argo 10-day intervals to determine the MLD were then confirmed by comparing those data with the station buoy daily means and the Argo monthly means. With respect to vertical and temporal resolutions, the Argo 10-day data has two distinct advantages: (1) improved representation of the MLD vertical change due to high vertical resolution, especially during periods of large MLD variability and (2) more detailed representation of the temporal change in MLD than achieved with the Argo monthly mean data, especially from winter to spring in mid and high latitudes. These advantages were maintained in the case of a larger threshold despite the fact that the MLD is rather deep and the detailed variation in its distribution differs depending on the season and location. This study also investigated the relative influence of TLD and PLD to the MLD calculation for each grid. Generally, the MLD is primarily determined based on the PLD at low and mid latitudes (TLD > PLD), whereas the TLD is more important at high latitudes, especially in winter (TLD < PLD). In the case of a larger threshold, the area of the larger PLD influence spreads polewards because of the greater effect of salinity in winter. Although there are some differences in the effect of temperature and salinity in estimations of the MLD, both are indispensable factors for the MLD estimations even at different thresholds.  相似文献   

Global surface layer salinity change detected by Argo and its implication for hydrological cycle intensification   总被引：1，自引：0，他引：1  

Shigeki Hosoda  Toshio Suga  Nobuyuki Shikama  Keisuke Mizuno 《Journal of Oceanography》2009,65(4):579-586

We investigated changes in the global distribution of surface-layer salinity by comparing 2003–2007 Argo-float data with annual mean climatological surface-layer salinity data for 1960–1989 from the World Ocean Database 2005. The two datasets showed similar patterns, with low values in subpolar and tropical regions and higher values in the subtropics. The recent Argo data indicate that the contrast between low and high salinity has intensified in all areas except the subpolar North Atlantic. The intensified contrast of the surface layer salinity was maintaining for 2003–2007. Using a simple method, we attempted to estimate evaporation and precipitation changes on the basis of surface-layer salinity changes. The results show a high probability that the global hydrological cycle has increased in the past 30 years.  相似文献