Hazard risk assessment of tropical cyclones based on joint probability theory

The main hazard-causing factors of tropical cyclones are strong wind,heavy rainfall,and storm surge.Evaluation of the hazard-causing degree of a tropical cyclone requires a joint intensity analysis of these hazard-causing factors.According to the maximum hourly mean wind speed,total rainfall,and maximum tide level at various observation stations in Hong Kong during these tropical cyclones,three hazard-causing indices for tropical cyclones are introduced:the strong-wind index(VI),total-rainfall index(RI),and tide-level index(LI).Through a joint probability analysis of VI,RI,and LI for a tropical cyclone affecting Hong Kong,the joint return period is calculated to evaluate its joint hazard-causing intensity.A limit state function of Hong Kong’s resistance to tropical cyclones is developed and used to evaluate the regional risk of tropical cyclones affecting Hong Kong.The results indicate that the joint return period of VI,RI,and LI can reflect the joint hazard-causing intensity of strong wind,heavy rain,and storm surge caused by tropical cyclones;if the overall design return periods of the regional structures decrease,the regional ability to defend against tropical cyclone disasters is degraded.

Risk Regionalization of Low-temperature Disasters for Flue-cured Tobacco Planting in Qujing Area Based on GIS

There is a prominent,complex and diverse three-dimensional climate and a variety of meteorological disasters in Qujing area. The risk zoning of low-temperature disasters for flue-cured tobacco planting in Qujing area was studied to provide reference for drawing on advantages and avoiding disadvantages in flue-cured tobacco planting,disaster reduction,and disaster relief services. According to the production practice of fluecured tobacco and local climate analysis,it was determined that flue-cured tobacco in Qujing area was very vulnerable to low temperature during the seedling stage（ from early February to middle April） and in the mature period（ from early July to early September）. Based on the quantitative analysis and evaluation of risk of disaster-causing factors,sensitivity of disaster-breeding environment,vulnerability of carriers,and disaster prevention and reduction capability,a risk assessment model of meteorological disasters was established to precisely evaluate and zone the risk of low-temperature disasters for flue-cured tobacco planting in allusion to the seedling and mature stage in Qujing area by using GIS technology. The risk of lowtemperature disasters for flue-cured tobacco planting during the two periods was divided into four grades,namely low,medium,high and very high risk.

Regionalization and the Method for Risk Grading for Flash Flood Disaster in Tibet Region

Flash flood is one of the major meteorological disasters on the Tibet Plateau (TP). Flash flood risk regionalization based on the theory of flash flood occurrence risk is the essential basis for relative risk management. The flash flood risk regionalization and the high-resolution grid mountain flood risk level in TP is carried out by using ArcGIS with the indicators of rainfall, days of heavy rain, vegetation cover, slope, relative elevation difference, river network density, population density, average GDP and traffic density. The areas with high mountain flood risk are mainly located in the middle and downstream of Yarlung, the Nujiang River Valley, the Jinsha River and Lancang River Basin. Besides, the results of flash flood disaster risk regionalization were tested by using historical flash flood disaster data and calamity census data. The disasters occurred in high-risk and sub-high-risk regions are accounted for 73%. Flash floods that cause casualties and economic losses of more than 100,000 CNY (Chinese Yuan) occurred in high-risk areas. Flash flood risk assessment may provide reference for the prevention and control of geological disasters in TP, improve disaster prevention and mitigation capabilities, reduce the hazards of flash floods to social development.

TYMS gene 5'-and 3'-untranslated region polymorphisms and risk of non-syndromic cleft lip and palate in an Indian population

Dear Editor： Increased homocysteine levels due to vitamin B6 or B12 deficiency or genetic defects in folate pathway genes are associated with an increased incidence of non-syndromic cleft lip with or without cleft palate （NSCLP）tlj. Thymidylate synthase （TS） is a folate-dependent enzyme that catalyzes methylation of 2＇-deoxyuridine-5＇-monophosphate （dUMP） to 2＇-deox- ythymidine-5＇-monophosphate （dTMP）, a rate-limiting step in DNA synthesis,

In search of potential earthquake source regions in the Chinese mainland in the light of ambient shear stress field

Earth media are incomplete media.There exist many cracks in it. The achievements of fracture mechanics showthat the strength of the incomplete materials will be much lower than that of the complete materials. We consider that earthquake occurrence is the result of unstable propagation of a crack in crust media in proper conditionand the earthquake rupture is the phenomenon of a failure by fast fracture under applied low shear stress. It hasalready been explained by fracture mechanics.The occurrence of failure by fast fracture is necessarily associated with the presence of high level concentration of local stress and strain. The elastic/plastic stress analysis in cracked pieces by Dugdale indicates that thestate of stress at the tip of a crack takes a very important role to crack propagation. A plastic zone has necessarilyformed in the tip of a crack due to stress concentration. Therefore, the dislocations st the tip of a crack are naturally a plastic displacement, rather than elastic one. The plastic displacement, where τ0 is appliedshear stress which is equivalent to initial or tectonic shear stress when the quake occurs, a is the half length of acrack, It is the rigidity,τy is the yield stresses in shear. The main seismic dislocations take place exactly at theends of the crack where the plastic zone had been formed. SO, a critical assumption is adopted, i. e. we assumethe dislocation D(1,,t) as formula (5) in text. The maximum earthquake dislocation, whereL is the fault length. If p is taken the value in the upper crust, μ=33 GPa; and τy is taken the average valuegiven from laboratories,τy= 30 MPa. Thus, according to observation values of Dmax and L, using the formula,one can estimate the initial shear stresses for large earthquakes. Computations show that the initial shear stressesfor large earthquakes all over the world are about 5-20 MPa which have some differences between regions.We further research the characteristics of source spectra and have derived the dependent relation of bodywave magnitude mb on the shear stress τ0 and seismic moment M, as formula (11)in text. Thus, the formulaprovides a POssibility of computation of large amount of tectonic shear stress values from seismic data. We consider that the tectonic shear stress field is a main factor which controls the earthquake occurrence. The regions withhigh tectonic shear stress values are considered to be prone to occur great earthquakes (Ms>6) and called earthquake hazard regions. Based on this criterion, τ0 values for all earthquakes with mb≥3. 8 all over China since1987 have been computed, and the great earthquake hazard regions with magnitude ranges have been zoned inthe Chinese mainland.During April 1992 -January 31, 1994, there were 9 Ms≥6 earthquakes which occurred in the Chinesemainland, 8 earthquakes of the 9 had fallen into the regions delineated by us prior to the earthquake occurrence,with only one failure. This new approach as a method for medium--term prediction of strong earthquakes hasbeen proved by practice to be an efficient one.It has good physical bases and bright prospect and worth furtherresearch. Received February 7,1994 1 Accepted February 10, 1995.Contribution No. 95A0061, Institute of Geophysics,SSB, China.

MathematicalsimulationofmoderateandstrongearthquakesequenceinZhujiangDeltaanditssurroundingareasinth

With the orthogonal design and the finite element methods, the outside stresses acting on the boundary and the inside tectonic stress field before the 1911 Honghai Bay earthquake are obtained. Under these stress fields, the dislocation patterns of the faults are consistent with the observed ones. Using the softening unstabilization model for elastoplastic media to simulate the process of the earthquake occurrence, 5 moderate and strong earthquakes in these areas in this century are simulated. The results show that the moderate or strong earthquake happened only at the sections of the faults whose fault safety degree is zero. According to the present distribution of the fault safety degree, the authors predict the seismic risk zones there.

不同全球变暖目标下中国气候变化风险区域格局

Climate change will bring huge risks to human society and the economy.Regional climate change risk assessment is an important basic analysis for addressing climate change,which can be expressed as a regional system of comprehensive climate change risk.This study establishes regional systems of climate change risks under the proposed global warming targets.Results of this work are spatial patterns of climate change risks in China,indicated by the degree of climate change and the status of the risk receptors.Therefore,the risks show significant spatial differences.The high-risk regions are mainly distributed in East,South,and central China,while the medium-high risk regions are found in North and southwestern China.Under the 2℃warming target,more than 1/4 of China’s area would be at high and medium-high risk,which is more severe than under the 1.5℃warming target,and would extend to the western and northern regions.This work provides regional risk characteristics of climate change under different global warming targets as a foundation for dealing with climate change.