利用GRACE重力卫星数据研究区域时变重力场及同震布格重力异常的变化特征

发布时间：2018-06-08 15:15

本文选题：布格重力异常 + 时变重力场　；参考：《长安大学》2017年硕士论文

【摘要】：卫星重力测量技术,以其范围广、定期更新、无困难地域限制、不受天气、地形、交通等环境因素影响的优点愈来愈得到广大地学工作者的重视。新一代重力卫星CHAMP、GRACE、GOCE等的发射,使得卫星重力技术在固体地球物理学、地质学、海洋测绘学、气象学以及空间大地测量学等学科的研究中发挥出至关重要的作用。大地震发生时常常伴随着地球深部构造的变化以及地下介质密度的改变。由于使用卫星重力数据所获得的时变重力场能够反映地球的深部构造特征,进一步计算得到的布格重力异常可以反映地下介质密度的不均匀变化,这使得利用卫星重力技术研究地震发生时的时变重力场及布格重力异常变化特征成为了可能。由于龙门山断裂带地区处于青藏块体和川东块体的过渡地带且多发大震,如汶川地震和芦山地震,而尼泊尔地区处于印度洋板块和亚欧板块的过渡地带且发生尼泊尔地震,考虑到龙门山断裂带地区和尼泊尔地区均受青藏块体运动的影响,且两个地区均有大地震的频繁发生,本文计算了龙门山断裂带地区和尼泊尔地区大震发生时的时变重力场及布格重力异常变化情况,以期研究大洋板块交界带地震与大陆内部次级块体间地震的共同点及差异。因此,本文利用卫星重力测量技术对多震区域时变重力场与布格重力异常的变化进行监测,研究了与青藏高原构造变形活动密切相关的区域的时变重力场的动态变化特征和布格重力异常的变化情况,探讨了区域构造运动与断层活动的关系。主要工作和成果如下:(1)本文在介绍GRACE卫星重力的基础上,讨论了卫星重力数据处理的理论方法与策略,重点推导了时变重力场与布格重力异常的计算方法,包括地球重力场、滤波原理、勒让德函数、GRACE卫星计算时变重力场和布格重力异常的流程等。(2)自主编程实现了勒让德函数标准前向列推法的计算,编写了基于GRACE月重力场模型计算时变重力场和重力异常的程序以及布格改正的程序,从而实现了对龙门山地区和尼泊尔地区时变重力场动态变化特征和布格重力异常变化的探索。(3)基于龙门山地区2008年与2013年的GRACE月重力场模型数据,结合该地区的地壳运动特征与地震活动情况,计算了龙门山地区时变重力场的变化情况,以及该地区重力异常的月变化与十年重力异常的变化情况。结果表明,从震前、震中到震后,龙门山断裂带地区时变重力场相应呈现“负-正-负”的变化趋势,结合地幔对流学说,推测其原因是,两次地震震前,断裂带区域震前壳幔物质较少且增速较慢,震中壳幔物质增多且增速变快,而震后壳幔物质变少增速变慢,这可能是震后位场变化回复理论的印证。(4)根据龙门山断裂带地区十年的布格重力异常变化得出,从2006到2015的十年之中,靠近西部青藏高原的断裂带西部地区总体以负异常为主,靠近东部四川盆地的部分总体以正异常为主,而龙门山地区基本处于二者的过渡范围中。推测是由于青藏高原物质流的东南向逃逸对龙门山断裂带地区造成的推挤导致的。(5)基于尼泊尔地区2015的月重力场数据,结合该地区的地壳运动特征与历史地震活动情况,计算了尼泊尔地区时变重力场的变化情况,以及该地区重力异常的月变化与十年变化情况。对尼泊尔地区时变重力场分析后发现,尼泊尔地区壳幔物质变多且物质增速快的地区呈现出由西北方向向东南方向转移的趋势。(6)分析尼泊尔地区2015年布格重力异常的月变化情况推测,尼泊尔地区北部处于负异常状态,这从侧面说明了由于印度洋板块对欧亚板块的碰撞挤压而产生的强烈挤压应力使得喜马拉雅地区长期处于俯冲挤压的状态,而包括加德满都在内的南部地区表现为正异常,则说明了尼泊尔地震引发了该地区板块的拉张,推测这与尼泊尔地区内部断层出现的南北向位移有关。由尼泊尔地区十年布格重力异常的变化情况得到,靠近喜马拉雅地区的尼泊尔西北部分则表现为正异常,这说明了喜马拉雅地区的地质地壳长期处于拉张与抬升的状态。
[Abstract]:Satellite gravity measurement technology, with its wide range, regular updates, no difficult geographical constraints, the advantages of the weather, terrain, traffic and other environmental factors have become more and more important. The launch of a new generation of gravity satellite CHAMP, GRACE, GOCE, etc. makes satellite gravity technology in Solid Geophysics, geology, and marine surveying and mapping Studies, meteorology, and spatial geodesy play an important role. Large earthquakes often occur with changes in the deep structure of the earth and the change of the density of the underground medium. The time varying gravity field obtained by using satellite gravity data can reflect the deep tectonic characteristics of the earth and further calculate the characteristics of the earth. The obtained Bouguer gravity anomaly can reflect the inhomogeneous change of the density of the underground medium, which makes it possible to use the satellite gravity technology to study the time-varying gravity field and the abnormal change characteristics of Bouguer gravity. The Longmen mountain fault zone is in the transition zone between the Qinghai Tibet block and the East Sichuan block and many large earthquakes, such as Wenchuan. In Sichuan and Lushan earthquakes, Nepal was located in the transition zone between the India and Eurasian plates and the Nepal earthquake occurred. Considering that the Longmen mountain fault zone and Nepal were affected by the movement of the Qinghai Tibet block, and the earthquakes occurred frequently in the two regions, the Longmen mountain fault zone and Nepal were calculated in this paper. In order to study the common points and differences between the boundary zone earthquakes of the oceanic plates and the secondary blocks within the continental continent, the variation of the time-varying gravity field and the Bouguer gravity anomaly during the occurrence of large earthquakes in the region are studied. The relationship between the dynamic changes of the time-varying gravity field and the variation of Bouguer gravity anomaly in the region closely related to the tectonic deformation activities of the Qinghai Tibet Plateau is discussed. The main work and results are as follows: (1) on the basis of the introduction of GRACE satellite gravity, the theory of satellite gravity data processing is discussed. On the basis of methods and strategies, the calculation methods of time-varying gravity field and Bouguer gravity anomaly are mainly derived, including the earth gravity field, filtering principle, Legendre function, GRACE satellite computing time variable gravity field and Bouguer gravity anomaly flow. (2) autonomous programming has realized the calculation of the Legendre number standard forward column method, and compiled a monthly weight based on the GRACE month weight. The force field model calculates the time-varying gravity field and gravity anomaly program and the bouge correction program, thus realizing the dynamic variation characteristics of the time-varying gravity field and the Bouguer anomaly change of the Longmen mountain and Nepal regions. (3) based on the GRACE month gravity field model data of the Longmen mountain area in 2008 and 2013, combined with this area The characteristics of the crustal movement and the seismicity have been calculated, and the variation of the time-varying gravity field in the Longmen mountain area, as well as the changes of the monthly and ten year gravity anomalies of the gravity anomaly in this area, show that the change trend of the time variable force field in the Longmen Mountain Fault zone shows a "negative positive negative" trend before the earthquake, the epicentral to the epicenter. According to the mantle convection theory, the reason is that before the two earthquake, the crust and mantle material was less and slower before the earthquake in the fault zone, and the crust and mantle material increased and increased rapidly in the epicenter, and the crust and mantle material became less slow after the epicenter. This may be the seal of the post seismic response theory. (4) according to the Bouguer weight of ten years in the Longmen Mountain Fault Zone In the ten years from 2006 to 2015, the western region near the Western Qingzang Plateau is dominated by negative anomalies, and the part of the eastern Sichuan basin is dominated by positive anomalies, while the Longmen mountain area is basically in the transition range of the two. It is presumed to be due to the southeast escape to the dragon of the Qinghai Tibet Plateau. (5) based on the data of the monthly gravity field of 2015 in Nepal area, combined with the characteristics of the crustal movement and historical seismicity in this area, the variation of the time-varying gravity field in the Nepal region, as well as the monthly and ten year changes of gravity anomalies in the region. After the analysis of the variable gravity field, it is found that the region of the crust and mantle material in the Nepal region is more and more rapidly increasing. (6) the monthly variation of the Bouguer gravity anomaly in Nepal area in 2015 is speculated that the north of Nepal is in a negative abnormal state, which shows from the side that the India ocean board is on the side. The strong extrusion stress produced by the collision and extrusion of the Eurasian plate makes the Himalaya region be in a state of subduction and extrusion for a long time, while the southern region, including Kathmandu, shows a positive anomaly. It shows that the Nepal earthquake triggered the extension of the plate in this area, which is conjectured to the north and south of the internal faults in the Nepal region. It is related to displacement. From the ten year Bouguer gravity anomaly in Nepal, the north-west part of Nepal near Himalaya shows a positive anomaly, which shows that the geological crust in the Himalaya region is in the state of stretching and lifting for a long time.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P223

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