CONSTRAINING THE FOCAL MECHANISM OF THE 2015 NEPAL EARTHQUAKE WITH OBSERVATIONS OF THE CONTINUOUS GRAVITY STATIONS          下载免费PDF全文

JIANG ying  LIU Zi-wei  LI Hui  ZHANG Xiao-tong  WEI-Jin  SHEN Chong-yang 《地震地质》2016,38(3):660-669

On 25 April 2015, a magnitude M_S8.1 interplate thrust earthquake ruptured a densely instrumented region of Nepal. After earthquake, the focal mechanism solutions of Nepal earthquake were provided by well-respected international earthquake research institutions based on different data and methods, which were different. We compared free oscillations observed by 18 spring gravimeters of continuous gravity stations with synthetic normal modes corresponding to 3 different focal mechanisms for the Nepal earthquake, and the focal mechanisms solutions of Nepal earthquake were analyzed and constrained by spherical normal modes in a 2 to 5mHz frequency band. Based on the optimal focal mechanism, the accurate magnitude was searched. The results show that the focal mechanism of Nepal earthquake can be estimated by spherical modes in the 2 to 5mHz frequency band. The synthetic modes corresponding to the focal mechanism determined by the GCMT Moment Tensor Solution showed agreement to the observed modes, the average of misfit factors F was 0.03, and the average of scaling factors was 1.04, which was closest to 1, suggesting that earthquake magnitudes predicted in this way can reflect the total energy released by the earthquake. Based on the focal mechanism solutions provided by GCMT, keeping the strike, dip, slip, depth constant, adjusting the scalar moment, the real scalar moment was searched. When the average of scaling factors was 1, the average of misfit factors F was only 0.03. After calculation, the scalar moment of Nepal earthquake was 8.09×10²⁰ Nm, and the corresponding magnitude was M_W7.91.  相似文献   

Smallholder farmers’ participation in climate change adaptation programmes: understanding preferences in Nepal     

Uttam Khanal  Clevo Wilson  Boon Lee  Viet-Ngu Hoang 《Climate Policy》2018,18(7):916-927

Globally, adaptation policies and programmes are being formulated to address climate change issues. However, in the agricultural sector, and particularly in least developed countries (LDCs), concerns remain as to whether these policies and programmes are consistent with farmers’ preferences. This study empirically investigates Nepalese farmers’ willingness to support the implementation of adaptation programmes. To this end, we first developed suggested adaptation programmes in accordance with the adaptation measures identified by LDCs in their National Adaptation Programmes of Actions. We then employed a choice experiment framework to estimate farmers’ willingness to pay (WTP) for adaptation benefits. The findings indicate that the substantial benefits of the adaptation programmes for farmers result in a sizeable WTP to participate, which would appear to justify the programmes’ widespread implementation.

Key policy insights

• Farmers are willing to participate in, and contribute to, the suggested adaptation programmes in the form of increased access to climate adaptive crop species and varieties, improved soil quality and irrigation and the provision of training in climate adaptive farming.

• Key socio-economic factors influence farmers’ support of adaptation programmes. Older farmers, those households closer to government extension services, larger land holders, those involved in household labour exchange, farmers located in drought and flood-prone regions and those who perceive that the climate has changed are more likely to participate.

• The more farmers are aware of climate change impacts, the greater their preference for adaptation programmes. Increasing farmer awareness prior to implementation of such programmes is therefore an obvious means of further raising participation rates.

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Chasing Chinese Caterpillar Fungus (Ophiocordyceps sinensis) Harvesters in the Himalayas: Harvesting Practice and Its Conservation Implications in Western Nepal     

Uttam Babu Shrestha  Sujata Shrestha  Shivaraj Ghimire  Kamal Nepali  Bharat Babu Shrestha 《社会与自然资源》2014,27(12):1242-1256

The Chinese caterpillar fungus is famous for its high market value, unusual life history, and significant medicinal uses. It is harvested by very poor communities and sold for an extraordinarily high price. Most of the studies on this species are focused on therapeutic uses, chemical analyses, ecology, and trade. However, harvesting techniques and intensity of the harvests remain undocumented. We document harvesting techniques, trends of harvest, and perceptions of the Chinese caterpillar fungus harvesters in Dolpa, Nepal, based on surveys, focus-group discussions, and direct observations. Along with increasing market value, intensity of the harvest has been increasing. The Chinese caterpillar fungus harvest has now become the second most important livelihood strategy for the local communities, after agriculture. Reported per-capita harvest based on the first day of collection has declined over the last 4 years, apparently because of the decline in the stock and the increasing number of harvesters.  相似文献   

基于2015年尼泊尔M_W7.8地震震后形变探测青藏高原南缘的岩石圈流变结构     

张健  赵斌  王东振  王海斌  刘志军 《大地测量与地球动力学》2021,41(8):827-832

基于有限元方法,采用2015年尼泊尔MW7.8地震震后5 a的GPS观测资料约束青藏高原南缘的岩石圈流变结构,利用通过主前缘逆冲断裂带(MFT)间的距离来约束边界位置的垂直边界结构和印度弹性俯冲板片结构探测印度板块和青藏高原板块的边界结构。结果表明,2种结构均能产生与观测数据一致的南-西南水平运动模式,并能较好地解释远场地面位移,但垂直边界结构模型得到的垂直形变偏大,而俯冲板片结构模型能很好地解释中尼边境及以北地区的隆升现象。青藏高原下地壳稳态和瞬态粘滞系数的最优结果分别为1×1018 Pa·s和1×1017 Pa·s。  相似文献   

基于GNSS观测研究2015年尼泊尔M_W7.8地震震后地壳形变特征及其机制     

姚未正  徐克科  朱绪林  邵振华 《大地测量与地球动力学》2021,41(8):833-840

收集及处理尼泊尔境内的GPS连续观测站和中国藏南地区的GPS基准站数据,获得2015年尼泊尔MW7.8地震震后3 a的GPS水平形变场。结果显示,尼泊尔地震的震后形变主要分布于尼泊尔北部及中尼边境区域,且东西方向形变较小,南北方向形变较大,整体继续向南运动,最大震后位移约为10.93 cm。采用孔隙弹性回弹模型计算的理论地表位移远小于GPS观测值,无法解释GPS观测到的震后形变。采用震后余滑模型反演的结果表明,震后余滑主要集中在断层的下倾延伸部分,且空间分布较广,余滑释放的地震矩为1.09×1020 Nm。采用PSGRN/PSCMP程序计算粘弹性引起的理论地表形变结果显示,粘弹性松弛模型不能解释近场GPS观测值,但在远场区域的运动方向与GPS观测值一致。采用粘弹性松弛和震后余滑组合机制模型进行反演,余滑释放的地震矩降为1.08×1020 Nm,且空间分布更加集中。研究结果表明,组合机制模型在保证了模型拟合精度的基础上,反演结果与应力驱动模型反演结果更接近。  相似文献   

GRACE卫星观测到的尼泊尔8.1级地震前后的重力变化     

瞿伟  安东东  薛康  张勤  王庆良  王栋 《大地测量与地球动力学》2017,37(12):1214-1218

利用GRACE卫星重力资料,计算尼泊尔地震震中及周缘重力和地表密度时空变化,并获取震源域特征点重力变化时间序列。结果表明,青藏高原内部、印度北部及华南块体东侧重力以增加为主,喜马拉雅与缅甸弧形带重力呈逐年减少趋势;尼泊尔地震发生在正负重力变化梯度带上,且重力变化在2015年具有明显的时间分段性特征,1~3月及地震发生的4月重力均以减小为主,5~9月以增加为主,12月以后以减小为主逐渐恢复;特征点时序揭示震源域重力呈长期减少趋势,并在2013~2016年呈现出“增加-减少-增加-发震-减小”的变化特征;地表密度变化较好地反映出地表质量迁移与重力变化的关系,为进一步理解尼泊尔地震的大陆动力学机制提供参考。  相似文献