Seismotectonics of Taiwan

High-quality seismicity data and focal mechanism solutions obtained during 1973–1983 by the permanent Taiwan Telemetered Seismographic Network and several temporary local seismographic networks are used for a detailed study of the seismotectonics of the Taiwan area. Seismicity distribution in southern Taiwan clearly reveals an east-dipping Benioff zone which has a thickness of about 30 km and begins to deepen along 121°E at a dip angle of 55°–60°. The leading edge of this Benioff zone reaches a depth of about 180 km between 21°N and 22°N, but tapers off to a shallower depth of about 100 km from 22°N to 23°N. The presence of this seismic zone implies that subduction of the South China Sea plate under the Philippine Sea plate extends from Luzon northward to about 23°N. The position of the northern boundary of the South China Sea plate, as tentatively defined according to the seismicity distribution, passes through southern Taiwan from the offshore area in the Taiwan Strait west of Kaohsiung in an east-northeast direction to the Taitung area where a triple junction probably lies. Seismicity is found to disappear abruptly below a certain depth in many parts of Taiwan. This phenomenon may be attributed to the frictional to quasiplastic transition in the crust or upper mantle. Comparison of shallow seismicity with surface faults and fractures shows that all areas of active shallow seismicity are marked by densely-developed faults and fractures. However, the converse is not necessarily true. This may be partly due to the relatively short duration of seismicity data and partly due to excessive weakening of some of the severely faulted and fractured areas. Finally, focal mechanism solutions for west central Taiwan and the Kuangfu-Fuli area in eastern Taiwan predominantly show a maximum horizontal compression in the SE-NW direction which can be related to collision between the Eurasian and Philippine Sea plates. However, focal mechanism solutions for both the Hualien area in eastern Taiwan and the Tainan area in southwestern Taiwan show remarkable irregularities which may result from local tectonic complexities.     

Measurement of ambient air particulate pollutant concentrations and dry depositions for PS-1 combined with dry deposition plate at a wetland site

In this study, the concentrations of ambient total suspended particulates (TSP) and their dry deposition were measured using a PS-1 sampler with dry deposition plates at a wetland sampling site in central Taiwan during a sampling period from October 2016 to December 2016. The PS-1 sampler was fixed at set distances (1.5 and 2 m) from a dry deposition plate, and sampled particulate pollutants were sampled to determine their concentrations and dry deposition rates simultaneously. A dry deposition plate 3 m from the PS-1 sampler was also used to collect dry deposition particulate. This plate was also used to compare dry depositions from ambient air, collected from new device. The results thus obtained indicated that the average dry deposition rates on the dry deposition plates that were 1.5 and 2 m from the sampler were 103.15 and 103.94 µg/m² min, respectively, in October, 83.36 and 100.18 µg/m² min in November, and 171.2 and 157.5 µg/m² min in December. These dry deposition rates were compared with that 3 m away from the PS-1 sampler. The statistical t test revealed no significant differences between the dry depositions on dry deposition plates at 1.5 and 2 m from the sampler. The dry deposition rates at 1.5 and 2 m from the sampler did not differ significantly from that at 3 m from the PS-1 sampler. This study proves that a PS-1 sampler can be combined with a dry deposition plate to measure TSP concentrations and dry depositions simultaneously using a single device.     

A probabilistic approach for earthquake risk assessment based on an engineering insurance portfolio

This paper presents the construction classification of the existing engineering covers in Taiwan. The exposure profile and variable vulnerability during different construction phases are established for some kinds of classes of construction. Finally, we present a method and framework to estimate the probable maximum loss of engineering insurance portfolio during an earthquake with consideration of the dynamic nature of structural changes and exposure values during a construction project.     

Spawning of major carps in the lower Halda River,Bangladesh

Spawning biology and spawn fishery of three valuable species of Indian major carps,Catla catla, Labeo rohita andCirrhinus mrigala, in the lower Halda River, Bangladesh, were studied in 1978. The major carps spawned only in the Sonairchar oxbow-bend from April to June on or near the dates of the full moon and the new moon. The tide was then at its highest level, and there was heavy flood water runoff from the hill region with sharp increases in water level, turbidity and current velocity, as well as decreases in water temperature, dissolved oxygen, and hydrogen ion concentration. These three heterogeneric species, as a result of parallelism or convergence in evolution, overlap in their environmental requirements for spawning. The nursery ground of the major carp fry spawned in the Halda River was found to be in the Bay of Bengal. The brood stock origin is suspected to be at the Shankha River, 40 miles south of the Karnafuli River. The spawn fishery in the Halda River was intensive but inefficient. Engineering works and water management schemes are threatening the spawning habitat.     

Deformation effects of porosity variation on soil consolidation caused by groundwater table decline

Soil consolidation has been widely analyzed using the poroelastic theory. As soil consolidation proceeds, porosity variation leads to the changes in hydraulic conductivity, Young’s modulus, and body force. However, the combined deformation effect of porosity variation on soil consolidation is rarely examined. In this study, a poroelastic consolidation model used to simultaneously consider the changes in hydraulic conductivity, Young’s modulus, and body force was developed to investigate the combined deformation effect of porosity variation on soil consolidation caused by groundwater table decline. The results indicate that the deformation effect of porosity variation on soil consolidation is negligible when the body force number is <0.01. For body force numbers >0.01, soil displacement could be overestimated or underestimated if the combined deformation effect of porosity variation is not completely considered. The misestimation of soil displacement increases as the body force number increases. In addition, the combined deformation effect of porosity variation also affects the transmission of pore water pressure. Therefore, it could be concluded that a reliable analysis of soil consolidation must simultaneously account for the variations in hydraulic conductivity, Young’s modulus, and body force.     

A research on the three-year performance of the regional emergency operation centers in Taiwan

For a smooth lateral integration between Taiwan’s regional emergency operation centers (EOCs) and with local health, fire, and medical units, the operating performance of the emergency medical care law (EMCL) needs to be enhanced throughout the emergency medical service system. In this article, a 3-year comprehensive evaluation was adopted to analyze the performance evaluation of six regional EOCs and to initiate a proposed framework with an appropriate coordinated operation and notification mode for the regional EOCs with above three units. The study discovered that establishing a closer coordinated operation and notification model relationship for the EOCs with above three units was a key factor to provide real-time information delivery and query services. A common disaster information and medical resource exchange platform should be established in the future, and the EMCL that allows EOCs to be the official dedicated units should be amended. In addition, EOCs must be given a regulatory power and responsibility to execute their services, which allows them to play an active role rather than a passive role. This would effectively help to integrate the fire, health, and medical units uniformly in the rescue response operation of disaster incidents.     

A wavelet based method for estimating the damping ratio in statnamic pile load tests

A wavelet based method is proposed to evaluate the time-dependent damping ratio in statnamic load tests by the continuous wavelet transform and half-power bandwidth method. The displacement along the pile during a statnamic test is described by a linear shape function, although the pile is assumed to be a single degree of freedom system (SDOF). The damping ratio is calculated by the half-power bandwidth method from the time–frequency spectra of continuous wavelet transform for the statnamic pile load test. A numerical simulation and two field statnamic tests were analyzed to verify the applicability of the proposed method, and the outcomes were compared with the results obtained using the unloading point method (UPM) and a method in literature. The damping ratio obtained with the proposed method is satisfactory and provides an additional interpretation measure for statnamic load tests.