东北第五地震活跃期结束时间及最大地震强度预测

本文在以往对东北地震大形势研究的背景上,基于1900年以来东北地区地震目录资料,利用多种分析方法,对该区地震活动规律及其发展趋势作了详细研究。结果认为,东北第五地震活跃期约到2008年结束,本活跃期最大地震强度为6级左右。     

A point hailfall classification based on hailpad measurements: The ANELFA scale

The ANELFA scale for hailfall intensity is proposed on the model of the 6-class Fujita scale for tornadoes. It is based on more than three thousand point hailfalls measured by hailpads over a 16-year period in France. The class number of a hailfall is determined by the integer value of the largest measured hailstone diameter in cm, or by equivalence with current objects: A0 to A5 for pea, grape, pigeon's egg, walnut, hen's egg, orange. The class number is followed by a plus or minus sign if the ground is significantly more or less than half-covered by hailstones respectively. When the scale is applied to the ANELFA data, a log-normal distribution is found for the class distribution, allowing the frequency determination of the upper class ever observed until now at the hailpad stations.     

Low Free-Field Accelerations of the 1999 Kocaeli Earthquake?

The August 17, 1999 Kocaeli earthquake ruptured the earths surface along 145 km and produced a magnitude of M_w=7.4. As expected for such an event Modified Mercalli intensities of typically IX and X in the vicinity of the fault were determined. Yet the observed accelerations at the five near-fault sites remained amazingly small with horizontal PGA values of 0.14 g to 0.4 g. We attempt to resolve the enigma by modeling surface ground motion with a finite-difference algorithm, utilizing two different rupture and slip histories derived from the strong-motion observations and translate the computed horizontal motion in intensity values. We can show that (a) in a given simple crustal velocity model different slip distributions result in significantly different ground motion distributions in the vicinity of the fault even though both slip distributions fit the observed accelerometer data quite well. (b) Both slip distributions project high ground motion into areas adjacent to the fault where no accelerometer was located. (c) Both slip distributions are not fully compatible with observed intensity observations around the fault, although this could be partly attributed to the lack of knowledge regarding to the crustal structure. In the light of our results it would thus be misleading if the few strong-motion observations around the Kocaeli earthquake fault were taken as typical or representative for the entire area and for potential future events.     

Regional Tectonic Deformation Background and Medium- and Short-Term Precursors to the Minle-Shandan Earthquakes

INTRODUCTIONOnOctober 2 5,2 0 0 3,twoearthquakesofMS6 .1andMS5.8hitMinleandShandanofGansuProvinceinsuccession (at 38.4°N ,1 0 1 .2°E ;and 38.4°N ,1 0 1 .1°E) .Theseismicfaultisthrustandleft lateraltheMinle DamayingfaultwhichstrikesEWandisaffiliatedtot…     

Reevaluation of the earthquakes of 10 March and 19 May 1951 in southern Spain

Damage and parameters of the earthquakes of 10 March and 19 May 1951 in southern Spain have been reevaluated. Data available do not allow accurate depth determinations and previous estimates of larger depths are not confirmed, so depths have been fixed at 30 km for both shocks. Magnitudes (Ms) have been determined as 5.4 and 5.6, respectively. Intensities estimated at 22 and 29 sites from contemporary documentary sources give maximum values of VI–VII and VI (EMS Scale), lower than previous estimates. The focal mechanism for the May shock is right-lateral strike-slip with a normal component of motion, with planes with strikes 273° and 169°; seismic moment 1.9 × 10¹⁶ Nm and dimension 6 km (radius of circular fault). Shocks are located near the boundary between the Iberian plateau and the Guadalquivir Basin and may be related to faults connected with this boundary.     

Effect of Horizontal Nonuniformity of Diabatic Heating on Tropical Cyclone Intensity and Structure

1. IntroductionMuch attention has been paid to the role playedby diabatic heating in the genesis and intensificationof tropical cyclone (TC). Based on a two-dimensionalprimitive equation model, Li (1984) proposed that theevolution of TC should be different if the maximumheating appears at different height. Yang et al. (1995)found that abrupt intensification of TC at the mid-latitudes is closely related to the vertical structure ofconvective heating. May and Holland (1998) suggestedthat the…     

Relationships between air mass properties and mesoscale rainfall in New Zealand's Southern Alps

This paper identifies relationships between air mass properties and mesoscale rainfall when moist air blows over New Zealand's Southern Alps from the Tasman Sea. Around 50% of the variance in six-hourly rain volumes summed across three separate cross-mountain raingauge transects and in six-hourly rain volume spilling across the alpine divide are statistically explained by the following properties of the approaching air mass: relative humidity, wind velocity normal to the mountains, air mass stability and synoptically induced upward motion. These factors also explain about 25% (r≈0.5) of the variance in the downwind distance reached by the spillover rainfall. For the highest 10% of six-hourly rainfalls, spillover distance and magnitude are negatively correlated with the 700 or 500 hPa temperature. Multiple linear regression equations suitable for predicting rainfall intensity and spillover are developed. A progression is described in the magnitude and depth of vertical motion and resulting condensation rates over the mountains as the properties of the incoming air mass evolve through a storm. These changes, together with greater downwind advection of ice particles compared to raindrops, explain the observed statistical relationships between the air mass properties and mountain rainfall.     

作用于台风系统的动力——热力因子分析

本文导出了台风运动,结构和强度变化的关系方程式,该式表明作用于台风系统的动力－热力因子同时影响台风运动,结构和强度的变化。本文还是导出了台风系统内凝结与降水的不平衡与台风运动的关系方程式,分析该方程所得结果与台风运动的一些实际情况和统计研究结果一致。