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71.
Crustal and upper mantle structure and the deep seismogenic environment in the source regions of the Lushan earthquake and the Wenchuan earthquake 总被引:11,自引:0,他引:11
Following the M w 7.9 Wenchuan earthquake, the M w 6.6 Lushan earthquake is another devastating earthquake that struck the Longmenshan Fault Zone (LFZ) and caused severe damages. In this study, we collected continuous broadband ambient noise seismic data and earthquake event data from Chinese provincial digital seismic network, and then utilized ambient noise tomography method and receiver function method to obtain high resolution shear wave velocity structure, crustal thickness, and Poisson ratio in the earthquake source region and its surroundings. Based on the tomography images and the receiver function results, we further analyzed the deep seismogenic environment of the LFZ and its neighborhood. We reveal three main findings: (1) There is big contrast of the shear wave velocities across the LFZ. (2) Both the Lushan earthquake and the Wenchuan earthquake occurred in the regions where crustal shear wave velocity and crustal thickness change dramatically. The rupture faults and the aftershock zones are also concentrated in the areas where the lateral gradients of crustal seismic wave speed and crustal thickness change significantly, and the focal depths of the earthquakes are concentrated in the transitional depths where shear wave velocities change dramatically from laterally uniform to laterally non-uniform. (3) The Wenchuan earthquake and its aftershocks occurred in low Poisson ratio region, while the Lushan earthquake sequences are located in high Poisson ratio zone. We proposed that the effect of the dramatic lateral variation of shear wave velocity, and the gravity potential energy differences caused by the big contrast in the topography and the crustal thickness across the LFZ may constitute the seismogenic environment for the strong earthquakes in the LFZ, and the Poisson ratio difference between the rocks in the south and north segments of the Longmenshan Fault zone may explain the 5 years delay of the occurrence of the Lushan earthquake than the Wenchuan earthquake. 相似文献
72.
一氧化氮和过氧化氢对万寿菊不定根形成的影响 总被引:1,自引:0,他引:1
以万寿菊(Tagetes erecta L.)为试材,研究了一氧化氮(NO)和过氧化氢(H2O2)对植物不定根形成中的影响及其相互关系。结果表明,外源NO供体肖普纳(SNP)和H2O2可显著地促进万寿菊外植体不定根的形成,且呈现明显的剂量效应,最适的SNP和H2O2浓度分别为50 μM和200 μM。NO和H2O2共同处理的万寿菊不定根的数量和根长显著高于NO或H2O2单独处理。NO在H2O2诱导万寿菊不定根形成的信号途径中起了重要作用;同时,H2O2包含在NO诱导不定根形成途径中。NO引起万寿菊外植体内源H2O2含量增加,H2O2亦促进内源NO积累。可见,NO和H2O2在万寿菊不定根形成过程中具有协同诱导效应,两者在促进不定根形成过程中可能通过互作反应提高各自的信号水平。 相似文献
73.
This paper studies the continuous evolution of breaking wave for the surface water waves propagating on a sloping beach. A Lagrangian asymptotic solution is derived. According to the solution coupled with the wave breaking criteria and the equations of water particles motion, the wave deformation and the continuous wave breaking processes for the progressive water waves propagating on a sloping bottom can be derived. A series of experiments are also conducted to compare with the theoretical solution. The results show that the present solution can reasonably describe the plunging or spilling wave breaking phenomenon. 相似文献
74.
Abstract— Here we report the petrography, mineralogy, and bulk compositions of Ca,Al‐rich inclusions (CAIs), amoeboid olivine aggregate (AOA), and Al‐rich chondrules (ARCs) in Sayh al Uhaymir (SaU) 290 CH chondrite. Eighty‐two CAIs (0.1% of the section surface area) were found. They are hibonite‐rich (9%), grossite‐rich (18%), melilite ± spinel‐rich (48%), fassaite ± spinel‐rich (15%), and fassaite‐anorthite‐rich (10%) refractory inclusions. Most CAIs are rounded in shape and small in size (average = 40 μm). They are more refractory than those of other groups of chondrites. CAIs in SaU 290 might have experienced higher peak heating temperatures, which could be due to the formation region closer to the center of protoplanetary disk or have formed earlier than those of other groups of chondrites. In SaU 290, refractory inclusions with a layered texture could have formed by gas‐solid condensation from the solar nebula and those with an igneous texture could have crystallized from melt droplets or experienced subsequent melting of pre‐existing condensates from the solar nebula. One refractory inclusion represents an evaporation product of pre‐existing refractory solid on the basis of its layered texture and melting temperature of constituting minerals. Only one AOA is observed (75 μm across). It consists of olivine, Al‐diopside, anorthite, and minor spinel with a layered texture. CAIs and AOA show no significant low‐temperature aqueous alteration. ARCs in SaU 290 consist of diopside, forsterite, anorthite, Al‐enstatite, spinel, and mesostasis or glass. They can be divided into diopside‐rich, Al‐enstatite‐rich, glass‐rich, and anorthite‐rich chondrules. Bulk compositions of most ARCs are consistent with a mixture origin of CAIs and ferromagnesian chondrules. Anorthite and Al‐enstatite do not coexist in a given ARC, implying a kinetic effect on their formation. 相似文献
75.
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77.
曾文水库保护带泰山滑坡之调查与治理 总被引:1,自引:0,他引:1
崩塌与滑坡灾害之治理,首重破坏诱因了了解与破坏机制之调查。再根据调查观测所得之资料与参数,着手进行设计适当之防治对策,方能得到良好的治理成效。泰山滑坡位于台湾南部极重要之曾文水库的保护带。其边坡由陆陆续续的崩陷而逐渐演变为坍滑,甚至造成交通中断受阻。调查发现本区为属浅层滑动,滑动区平面类似酒瓶状,主要原因为长期受到雨水之漫流与渗透软化的影响,加上蚀沟之切割淘刷作用,使得边坡容易失去支撑而滑动。经施以经济有效的蚀沟控制工程兴建多座潜坝,跌水与排水设施后,发现确定提高了边坡之稳定性,地区产业因而可以持续动作,是一次相当成功的治理案例模式,但由于施工便道之开 当,遂再度诱发部份边坡的坍滑,故尔后之维护管理工作极为重要。 相似文献
78.
79.
Satellite-derived data of the outgoing longwave radiation(OLR), net shortwave radiation at the tropopause(SRT)and circulation information as predicted by NCEP are used in the work to study seasonal variations of net radiative heating in the earth-atmospheric system and its relationship with the Asian summer monsoon. As is shown in the result, the zonal deviations of the zonal deviations of the heating, manifested as mutations in direction between land and sea with seasons, is an indication of the thermal difference between them. Being a month earlier than that in the general circulation from spring to summer, the seasonal reversal of directionmay be playing an essential role in triggering the onset and withdrawal of summer monsoon in Asia. 相似文献
80.