利用格点化降水观测数据集(CN05.1)以及ECMWF再分析资料(ERA5),分析1961—2020年夏季西南地区东部(Eastern Southwest China,ESWC)的降水、水汽含量及降水转化率特征,并利用天气学分析方法初步探究地形分布对降水转化率空间分布差异的影...利用格点化降水观测数据集(CN05.1)以及ECMWF再分析资料(ERA5),分析1961—2020年夏季西南地区东部(Eastern Southwest China,ESWC)的降水、水汽含量及降水转化率特征,并利用天气学分析方法初步探究地形分布对降水转化率空间分布差异的影响,最后利用中尺度数值模式WRF4.0(Weather Research and Forecasting Model)设计地形敏感性试验验证地形对西南地区东部夏季降水的作用。结果表明:(1)1961—2020年夏季西南地区东部的降水呈现东多西少的分布特征,但水汽含量却在其东南部和西北部存在两个大值区,水汽大值区降水转化率偏低,强降水区与水汽含量大值区分布存在明显差异,通过分析强降水区与水平风场及垂直速度场的形势配合发现地形是导致此差异的重要因素。(2)WRF模式能较好地模拟出西南地区东部夏季降水的空间分布特征,通过地形敏感性试验发现,区域内大娄山、方斗山及大巴山组成的西南-东北向山地地形分布对降水强度有显著影响,地形高度的降低将导致区域东南部降水量显著减少。(3)敏感性试验中将区域地形高度分别降低一半和去除地形后,区域东南部的降水在月时间尺度中将分别减少9.89%和19.90%。地形高度的改变也会引起区域垂直速度、水平风场、水汽输送及水汽辐合量发生改变,当地形高度降低后,上升运动及西南风明显减弱,水汽输送强度降低,水汽辐合量减少,不利于降水形成。展开更多
In situ stress measurement data was analyzed to estimate the temporal and spatial stress variations at shallow depths in the Longmenshan fault zone(LMSF),prior to and following the 2008 Wenchuan earthquake(WCEQ).Analy...In situ stress measurement data was analyzed to estimate the temporal and spatial stress variations at shallow depths in the Longmenshan fault zone(LMSF),prior to and following the 2008 Wenchuan earthquake(WCEQ).Analysis of the stress field related to fault strength and behavior is useful for understanding geodynamic processes and conducting hazard assessments.The shallow stress changes after the WCEQ show clear along-strike variations.Degrees of stress orientation rotations have a negative correlation with the horizontal principal stress ratios and the WCEQ apparently reduced the magnitude difference between horizontal principal stresses.Taking stress magnitudes and orientation distribution relative to the fault strike into account,we propose an intermediate-strength of LMSF,with a friction coefficient generally constrained between 0.35 and 0.6.In addition,high-pressure fluids in the fault zone reduce the effective normal stress and to a certain degree weaken the fault strength.The accumulated stress over a certain period following release of the WCEQ indicates the start of another earthquake cycle.The changing crustal stress field makes the LMSF stable or slipping optimally during geodynamic processes.The segmentation feature of the shallow crustal stress field in the LMSF may imply a different tectonic loading and seismic release processes along the fault.The southwestern section to the epicenter of the WCEQ favors the occurrence of future earthquakes,as highμm in a state of critical failure was present in this area,which indicates that the Wenchuan and Lushan earthquakes did not release the accumulated stress to a sufficient extent there.展开更多
新生代印度—欧亚板块持续碰撞导致了青藏高原的隆升及陆内大型边界断裂的形成(Yin and Harrison,2000).阿尔金断裂系是地球上规模最大的走滑断裂系统之一(Molnar and Dayem,2010),长1600 km,由NEE走向的阿尔金左旋断裂和北侧的北阿尔...新生代印度—欧亚板块持续碰撞导致了青藏高原的隆升及陆内大型边界断裂的形成(Yin and Harrison,2000).阿尔金断裂系是地球上规模最大的走滑断裂系统之一(Molnar and Dayem,2010),长1600 km,由NEE走向的阿尔金左旋断裂和北侧的北阿尔金断裂以及两断裂之间夹持的菱形阿尔金山脉组成(Cowgill et al.,2003).作为青藏高原北缘主控边界,阿尔金断裂系统在印度—欧亚板块碰撞过程中对高原地壳变形起到了重要的调节作用.一种观点认为阿尔金断裂表现为左旋走滑运动,而北阿尔金断裂表现为逆性质为主,左旋走滑量有限,小于30 km(Yue and Liou,1999;Yue et al.,2004).另一种观点认为,阿尔金断裂与北阿尔金断裂均为左旋走滑断裂,且北阿尔金断裂的左旋位移量超过120 km(Cowgill et al.,2000,2003;Yin et al.,2002).近年更有研究认为北阿尔金断裂在中新世中期由左旋走滑转变为逆冲断裂(Gao et al.,2022).展开更多
文摘利用格点化降水观测数据集(CN05.1)以及ECMWF再分析资料(ERA5),分析1961—2020年夏季西南地区东部(Eastern Southwest China,ESWC)的降水、水汽含量及降水转化率特征,并利用天气学分析方法初步探究地形分布对降水转化率空间分布差异的影响,最后利用中尺度数值模式WRF4.0(Weather Research and Forecasting Model)设计地形敏感性试验验证地形对西南地区东部夏季降水的作用。结果表明:(1)1961—2020年夏季西南地区东部的降水呈现东多西少的分布特征,但水汽含量却在其东南部和西北部存在两个大值区,水汽大值区降水转化率偏低,强降水区与水汽含量大值区分布存在明显差异,通过分析强降水区与水平风场及垂直速度场的形势配合发现地形是导致此差异的重要因素。(2)WRF模式能较好地模拟出西南地区东部夏季降水的空间分布特征,通过地形敏感性试验发现,区域内大娄山、方斗山及大巴山组成的西南-东北向山地地形分布对降水强度有显著影响,地形高度的降低将导致区域东南部降水量显著减少。(3)敏感性试验中将区域地形高度分别降低一半和去除地形后,区域东南部的降水在月时间尺度中将分别减少9.89%和19.90%。地形高度的改变也会引起区域垂直速度、水平风场、水汽输送及水汽辐合量发生改变,当地形高度降低后,上升运动及西南风明显减弱,水汽输送强度降低,水汽辐合量减少,不利于降水形成。
基金supported by the National Natural Science Foundation of China(Grant No.41702351)the China Geological Survey Project(Grant Nos.DD20211376,DD20221816)。
文摘In situ stress measurement data was analyzed to estimate the temporal and spatial stress variations at shallow depths in the Longmenshan fault zone(LMSF),prior to and following the 2008 Wenchuan earthquake(WCEQ).Analysis of the stress field related to fault strength and behavior is useful for understanding geodynamic processes and conducting hazard assessments.The shallow stress changes after the WCEQ show clear along-strike variations.Degrees of stress orientation rotations have a negative correlation with the horizontal principal stress ratios and the WCEQ apparently reduced the magnitude difference between horizontal principal stresses.Taking stress magnitudes and orientation distribution relative to the fault strike into account,we propose an intermediate-strength of LMSF,with a friction coefficient generally constrained between 0.35 and 0.6.In addition,high-pressure fluids in the fault zone reduce the effective normal stress and to a certain degree weaken the fault strength.The accumulated stress over a certain period following release of the WCEQ indicates the start of another earthquake cycle.The changing crustal stress field makes the LMSF stable or slipping optimally during geodynamic processes.The segmentation feature of the shallow crustal stress field in the LMSF may imply a different tectonic loading and seismic release processes along the fault.The southwestern section to the epicenter of the WCEQ favors the occurrence of future earthquakes,as highμm in a state of critical failure was present in this area,which indicates that the Wenchuan and Lushan earthquakes did not release the accumulated stress to a sufficient extent there.
文摘新生代印度—欧亚板块持续碰撞导致了青藏高原的隆升及陆内大型边界断裂的形成(Yin and Harrison,2000).阿尔金断裂系是地球上规模最大的走滑断裂系统之一(Molnar and Dayem,2010),长1600 km,由NEE走向的阿尔金左旋断裂和北侧的北阿尔金断裂以及两断裂之间夹持的菱形阿尔金山脉组成(Cowgill et al.,2003).作为青藏高原北缘主控边界,阿尔金断裂系统在印度—欧亚板块碰撞过程中对高原地壳变形起到了重要的调节作用.一种观点认为阿尔金断裂表现为左旋走滑运动,而北阿尔金断裂表现为逆性质为主,左旋走滑量有限,小于30 km(Yue and Liou,1999;Yue et al.,2004).另一种观点认为,阿尔金断裂与北阿尔金断裂均为左旋走滑断裂,且北阿尔金断裂的左旋位移量超过120 km(Cowgill et al.,2000,2003;Yin et al.,2002).近年更有研究认为北阿尔金断裂在中新世中期由左旋走滑转变为逆冲断裂(Gao et al.,2022).
