2023年全球重大天气气候事件

2023年,全球平均气温比工业化前高出约1.45℃(±0.12℃),是有观测记录以来最热的一年。全球海平面继续上升,且全球平均海平面达到了有卫星记录(1993年至今)以来的最高水平,反映了持续的海洋变暖以及冰川和冰盖的融化。北极海冰面积仍远低于常年值,南极海冰面积创下历史新低。巴基斯坦、中国京津冀地区、意大利、巴西圣保罗州北部沿海地区、新西兰北岛等地遭受暴雨洪涝灾害,非洲西北部、中国云南、中美洲和南美洲北部发生严重干旱,南欧、北美、南美、东亚和南亚等地遭遇创纪录高温热浪,欧洲和北美等地遭遇寒流和暴风雪侵袭,强对流天气频繁袭击世界各处,全球热带气旋活动频繁。     

稳态瑞利波勘探的探测深度及影响因素分析

稳态瑞利波勘探所能达到的勘探深度是众多使用者越来越关心的话题。作者依据瑞利波勘探的基本原理和多年的实践经验,对影响勘探深度的各种因素,包括岩层的平均速度vR、使用的最低频率fmin、震源能量、各种地质因素、耦合因素等一一作了分析,并列举了多种条件下勘探深度的实际数据。指出综合运用合理参数,进一步提高对小异常的识别能力,有可能在目前基础上把瑞利波方法的勘探深度再提高一步。     

钻井中首波的共振与衰减

本文从P波首波的严格割线积分出发,首次给出了揭示其共振与衰减特性的渐近展开式,通过数值计算,对这些公式进行了检验,证明它们与严格解符合的相当好.解析的和数值结果一致表明:首波具有共振特性,频谱是连续的;振幅随源距z按1/z规律衰减;各共振峰幅度随岩石泊松比v的增大按[v/（1-v）]2规律增大.时域计算表明,所谓“滤波效应”正是首波共振激发特性的反映,传播过程中不频散.     

中层耗散大气中Rossby波包的非线性相互作用理论

采用弱非线性近似得出中层耗散大气连续谱Ｒｏｓｓｂｙ波包的非线性时空演化方程,讨论了Ｒｏｓｓｂｙ波包的三波相互作用问题．数值计算表明,耗散和非线性的共同效应决定了Ｒｏｓｓｂｙ波包的演变．当一个Ｒｏｓｓｂｙ波包通过大气传播时,它的振幅若超过某个阈值,空间尺度分别比它大和比它小的两个次级Ｒｏｓｓｂｙ波包的振幅会随时间增长．特别当这两个次级波包同时随时空变化时,仅当主波的振幅超过一个更大的阈值,且其群速度介于两次级波包的群速度之间时,两次级波包的振幅才会随时空同时增长,即出现绝对不稳定现象,耗散和３个波包的频率失配都会增大不稳定的阈值．     

Simulation of the direct runoff hydrograph at basin outlet

A simple model describing the transformation of effective rainfall to direct runoff through the overland flow mechanism is presented. The model is based on the classical representation of a watershed by a combination of planes and channels. The dynamics of overland flow in each plane is simulated by the non-linear kinematic wave, but the outflow from a given plane is concentrated in the middle of the corresponding drainage channel. The water routing in the channels is carried out by a piece-wise linearized formulation in space of the kinematic wave approximation. Using synthetic events on 10 watersheds, the model was tested by comparing it with results obtained by applying the non-linear kinematic wave to all the elements of the watershed. The model was found to be adequate, even in a form that simplifies the geometric features of the planes through an averaging procedure based on the Horton–Strahler ordering scheme of the watershed. © 1998 John Wiley & Sons, Ltd.     

滑坡的摩擦力与正压力力偶的地震波场模拟

滑坡的地震波反演是确定滑坡动力学过程的有效途径.然而,目前的滑坡地震波反演大多基于点源模型,将滑坡面近似为点源,仅考虑滑体作用于滑床的摩擦力及其变化.但实际滑坡过程中,由于重力和滑动距离的存在,滑床还受到一个逐渐增加的正压力力偶作用.为定量探讨这一正压力力偶对滑坡地震波场的贡献,我们基于有限滑坡面模型,分别正演模拟了滑坡过程中摩擦力和正压力力偶的地震波场,得到了正压力力偶地震波场在整个滑坡地震波场中的能量比例及其随距离的变化.研究发现,正压力力偶地震波场具备近场项衰减特征,相较于摩擦力波场随距离衰减更快.正演模拟显示,正压力力偶地震波场在滑坡尺度2~3倍距离范围内较为显著;但在更远距离上,由于其幅度大致随距离的平方衰减,其贡献几可忽略.此外,正压力力偶波场在波形特征上与摩擦力波场也存在明显区别,二者的相对大小与摩擦系数和坡度等参数密切相关.本文模拟分析表明,完整的滑坡近场地震波场应该同时考虑摩擦力和正压力力偶的贡献;滑坡动力学参数反演中,利用近场地震波记录,考虑有限尺度的滑坡面,原则上我们不仅可以确定传统滑坡动力学参数,还有可能确定摩擦系数和流体压力等参数在空间上的变化分布.

     

Spatial-temporal characterization of the San Andreas Fault by fault-zone trapped waves at seismic experiment site,Parkfield, California

In this article, we review our previous research for spatial and temporal characterizations of the San Andreas Fault (SAF) at Parkfield, using the fault-zone trapped wave (FZTW) since the middle 1980s. Parkfield, California has been taken as a scientific seismic experimental site in the USA since the 1970s, and the SAF is the target fault to investigate earthquake physics and forecasting. More than ten types of field experiments (including seismic, geophysical, geochemical, geodetic and so on) have been carried out at this experimental site since then. In the fall of 2003, a pair of scientific wells were drilled at the San Andreas Fault Observatory at Depth (SAFOD) site; the main-hole (MH) passed a ～200-m-wide low-velocity zone (LVZ) with highly fractured rocks of the SAF at a depth of ～3.2 km below the wellhead on the ground level (Hickman et al., 2005; Zoback, 2007; Lockner et al., 2011). Borehole seismographs were installed in the SAFOD MH in 2004, which were located within the LVZ of the fault at ～3-km depth to probe the internal structure and physical properties of the SAF. On September 282004, a M6 earthquake occurred ～15 km southeast of the town of Parkfield. The data recorded in the field experiments before and after the 2004 M6 earthquake provided a unique opportunity to monitor the co-mainshock damage and post-seismic heal of the SAF associated with this strong earthquake. This retrospective review of the results from a sequence of our previous experiments at the Parkfield SAF, California, will be valuable for other researchers who are carrying out seismic experiments at the active faults to develop the community seismic wave velocity models, the fault models and the earthquake forecasting models in global seismogenic regions.     

Crust and Upper Structure of Qinghai-Tibet Plateau and Its Adjacent Regions From Surface Waveform Inversion

CRUST AND UPPER STRUCTURE OF QINGHAI-TIBET PLATEAU AND ITS ADJACENT REGIONS FROM SURFACE WAVEFORM INVERSION