A multi‐azimuth seismic refraction study for a horizontal transverse isotropic medium: physical modelling results

To investigate the characteristics of the anisotropic stratum, a multi‐azimuth seismic refraction technique is proposed in this study since the travel time anomaly of the refraction wave induced by this anisotropic stratum will be large for a far offset receiver. To simplify the problem, a two‐layer (isotropy–horizontal transverse isotropy) model is considered. A new travel time equation of the refracted P‐wave propagation in this two‐layer model is derived, which is the function of the phase and group velocities of the horizontal transverse isotropic stratum. In addition, the measured refraction wave velocity in the physical model experiment is the group velocity. The isotropic intercept time equation of a refraction wave can be directly used to estimate the thickness of the top (isotropic) layer of the two‐layer model because the contrast between the phase and group velocities of the horizontal transverse isotropic medium is seldom greater than 10% in the Earth. If the contrast between the phase and group velocities of an anisotropic medium is small, the approximated travel time equation of a refraction wave is obtained. This equation is only dependent on the group velocity of the horizontal transverse isotropic stratum. The elastic constants A₁₁, A₁₃, and A₃₃ and the Thomsen anisotropic parameter ε of the horizontal transverse isotropic stratum can be estimated using this multi‐azimuth seismic refraction technique. Furthermore, under a condition of weak anisotropy, the Thomsen anisotropic parameter δ of the horizontal transverse isotropic stratum can be estimated by this technique as well.     

Sources of water in the Taiwan Strait

The conveyor of the source water that feeds into the Taiwan Strait (TS), particularly from the south, is investigated using historical CTD (Conductivity-Temperature-Depth) data and a North Pacific Ocean and East Asian seas coupled model. The modeled currents and drifter trajectories suggest that the Kuroshio Branch Water (KBW) rarely flows directly into the TS from the Luzon Strait (LS) in winter; instead the massive westward movement of the Kuroshio conveys high salinity water to the southeastern TS through a loop-like route. In summer, the modeled flow fields suggest that the Kuroshio surface currents hardly intrude into the TS directly from the LS. Observations and model results show that the monsoon-driven northeastwardflowing currents in the northern South China Sea transport relatively low salinity water through the entire TS.     

Typhoon-induced strong surface flows in the Taiwan strait and pacific

Surface Velocity Program drifters drogued at 15 m depth were deployed in the Taiwan Strait (TS) and Luzon Strait in 2005 and 2006. Several drifters in the TS and the Pacific were fortuitously overrun by the typhoon Hai-Tang (July 2005) and Shan-Shan (September 2006), respectively. The drifter and QuikSCAT wind data clearly demonstrate that the surface current over the TS and the Pacific can change dramatically for a period of about two days due to the strong winds of a typhoon during its passage. Our results show that the area of storm-affected surface currents is considerably smaller for a weaker typhoon (category 2 Shan-Shan), about 300∼400 km in radius, than for a stronger typhoon (category 5 Hai-Tang), about 800 km in radius. The maximum observed current speed in the TS was 1.7 ms⁻¹ (or 2.2 ms⁻¹ in net speed change) under the influence of Hai-Tang, and 2 ms⁻¹ in the Pacific under the influence of Shan-Shan. Drifter observations revealed the unusual phenomenon of flow reversal in the surface layer of TS and the Kuroshio induced by the typhoon passage. The effect of a typhoon on surface flows is amplified by the long, narrow geometry of the TS. Surface currents generated by wind forcing along the passage of a traveling typhoon can be explained by the Ekman drift.     

钝顶螺旋藻C-藻蓝蛋白分子内不同基团间能量传递的研究

于１９９６年８－１２月,从钝顶螺旋藻中分离纯化Ｃ－藻蓝蛋白,并用荧光光谱法对Ｃ－藻蓝蛋白分子内不同基团间的能量传递进行研究,结果表明,Ｃ－藻蓝蛋白分子内芳香族氨基酸残基能将能量传至与脱辅基蛋白共价结合的色基,从而使色基产生相应的荧光,Ｃ－藻蓝蛋白分子２４０－２４５ｎｍ的荧光激发峰产生于二硫键,它也能将吸收的能量传至色基;同时还发现,溶液状态下的Ｃ－藻蓝蛋白分子内,色氨酸残基可能位于分子内部的疏水区     

青藏高原南缘2015年尼泊尔MW7.8地震发震构造

2015年4 月25 日尼泊尔M_W7.8特大地震发生在喜马拉雅山南麓, 震源机制解表明该地震为低角度逆冲型地震.通过收集地震区的活动构造研究资料、卫星影像解释和野外实地考察,认为尼泊尔M_W7.8地震区地表分布三条主要的逆冲断裂,由北向南分别为喜马拉雅主中央断裂(MCT)、喜马拉雅主边界断裂(MBT)和喜马拉雅主前缘断裂(MFT).主边界断裂和主前缘断裂为晚更新世以来的活动断裂,但至今为止也没有发现喜马拉雅主中央断裂晚第四纪活动的依据.野外调查未发现尼泊尔M_W7.8地震在喜马拉雅山南麓的主要断裂上形成地震地表破裂带.喜马拉雅山南麓的构造特征为薄皮构造,表现为浅部陡倾断坡-深部缓倾断坪(7°左右)-深部断坡(11°左右)的构造样式.深部断坡-断坪又称为主喜马拉雅断裂(MHT),其中的深部断坡是尼泊尔地震主震(M_W7.8)和最大余震(M_W7.3)的发震构造.余震大致沿北西向的高喜马拉雅山前缘呈条带状分布,主要分布在低喜马拉雅山区内.剖面上,余震大致分布在主喜马拉雅断裂的上盘推覆体内,推测尼泊尔M_W7.8地震时深部断坡发生错动,其地震位移沿深部断坡-断坪向南传播引起上盘的褶皱带缩短变形,进而触发低喜马拉雅和次喜马拉雅褶皱带内产生次级破裂从而产生余震.     

An inter-hemispheric comparison of the tropical storm response to global warming

Model studies do not agree on future changes in tropical cyclone (TC) activity on regional scales. We aim to shed further light on the distribution, frequency, intensity, and seasonality of TCs that society can expect at the end of the twenty-first century in the Southern hemisphere (SH). Therefore, we investigate TC changes simulated by the atmospheric model ECHAM5 with T213 (~60 km) horizontal resolution. We identify TCs in present-day (20C; 1969–1990) and future (21C; 2069–2100) time slice simulations, using a tracking algorithm based on vorticity at 850 hPa. In contrast to the Northern hemisphere (NH), where tropical storm numbers reduce by 6 %, there is a more dramatic 22 % reduction in the SH, mainly in the South Indian Ocean. While an increase of static stability in 21C may partly explain the reduction in tropical storm numbers, stabilization cannot alone explain the larger SH drop. Large-scale circulation changes associated with a weakening of the Tropical Walker Circulation are hypothesized to cause the strong decrease of cyclones in the South Indian Ocean. In contrast the decrease found over the South Pacific appears to be partly related to increased vertical wind shear, which is possibly associated with an enhanced meridional sea surface temperature gradient. We find the main difference between the hemispheres in changes of the tropical cyclones of intermediate strength with an increase in the NH and a decrease in the SH. In both hemispheres the frequency of the strongest storms increases and the frequency of the weakest storms decreases, although the increase in SH intense storms is marginal.     

Estimating the economic impacts of climate change on infectious diseases: a case study on dengue fever in Taiwan

Researchers of climate change have suggested that climate change and variability has a significant influence on the epidemiology of infectious diseases, particularly vector-borne diseases. The purpose of this study is to explore how climate conditions and the dengue fever epidemic in Taiwan are related and to estimate the economic impact of climate change on infectious diseases. To achieve these objectives, two different methods, one involving the Panel data model and the other the Contingent Valuation Method (CVM), are applied in this study. At first, we use the Panel data model to assess the relationship between climate conditions and the number of people infected by dengue fever during the period from January 2000 to February 2006 in 308 cities and townships in the Taiwan. The results of the empirical estimation indicate that climate conditions have an increasingly significant impact on the probability of people being infected by dengue fever. The probability of being infected by dengue fever due to climate change is then calculated and is found to range from 12% to 43% to 87% which represent low, mid, and high probabilities of infection caused by climate change when the temperature is increased by 1.8°C. The respondent’s willingness to pay (WTP) is also investigated in the survey using the single-bounded dichotomous choice (SBDC) approach, and the results show that people would pay NT$724, NT$3,223 and NT$5,114 per year in order to avoid the increased probabilities of 12%, 43%, and 87%, respectively, of their being infected with dengue fever.