【作者】 季灵运；

【导师】 许建东； 王庆良；

【作者基本信息】 中国地震局地质研究所 ， 构造地质学， 2012， 博士

【摘要】 位于中朝边界的长白山天池火山是一座具有潜在灾害性喷发的大型近代活动火山。长白山天池火山历史上发生了多次喷发事件，曾造成了巨大的灾难，发生在公元946年的大喷发，就规模和猛烈程度而言，属于全球近2000年以来最大的爆炸喷发之一。鉴于此，“九五”和“十五”期间，中国地震局等几家单位对长白山天池火山进行了较为系统的地质、地球物理探测研究，并进行了以地震活动、形变、地球化学变化为主的固定、流动台网监测研究工作，取得了很多有益的成果，但这些常规的监测方法由于受到天池火山地理位置的特殊性（跨国境）、工作条件的复杂性（原始森林、天池湖水）等限制，虽耗费了大量人力物力，但至今天池火山区下部的浅层岩浆统在什么位置、如何展布等问题，一直没有探测认识清楚。也有学者基于GPS、水准的形变监测资料进行了岩浆房参数的反演工作，但由于点距的稀疏性，各个学者给出的岩浆房参数不尽一致，存在争议。常规手段的监测结果表明，长白山天池火山2002‐2006年发生了较明显的岩浆异常扰动事件，但其机理尚不明确。另外，我国缺少现今正在喷发的活动火山，火山岩浆系统的存储、供给与运移动力机制研究方面比较薄弱。InSAR（Interferometric Synthetic Aperture Radar，合成孔径雷达干涉测量）技术是近二十年发展起来的全新空间对地观测技术，能够以较高的时间、空间分辨率对地表实现大范围监测，具有其他大地测量手段无法比拟的优势。此外，作为遥感领域的一个重要分支，卫星热红外遥感技术以其安全、有效、宏观、周期性地远距离对地观测的优势，已经广泛应用于各种类型的地表热变化监测。基于InSAR技术和卫星热红外遥感技术的优势，本文以长白山天池火山为主要研究对象，开展了两种技术在火山领域的应用与相关研究。主要研究内容如下：1.长白山天池火山的形变背景：收集了我国东北、华北、华南地区1999‐2007年的GPS水平速度场，以及日本及周边地区2000‐2010年的GPS速度场；从国家测绘局大地测量数据处理中心收集了我国东北地区上世纪70、90年代两期一等水准测量资料，采用以水准点间高差变化速率即速率差为观测值、以观测点速率为未知参数的垂直形变网整体平差方法，计算得到了我国东北地区长期地壳垂直形变速率；2.利用PSInSAR技术监测长白山天池火山近年来的形变演化：本文基于18景ENVISAT ASAR影像资料，利用PSInSAR技术获取了天池火山2004‐2010年的形变时间序列，结果与同期的水准测量结果吻合的较好，表明PSInSAR可以以毫米级的精度监测火山区地表形变。然后基于考虑地形影响的Mogi模型模拟了PSInSAR获取的累积形变场，确定了浅层岩浆房的空间位置；3.利用卫星热红外遥感技术监测长白山天池火山热异常：建立了基于Landsat TM/ETM和ASTER热红外波段遥感影像监测火山热活动的技术方法体系：首先，分别利用单窗算法和温度/比辐射率分离算法反演基于Landsat TM/ETM和ASTER热红外波段遥感影像的区域地表温度，然后分别计算不同地表覆盖类型的温度平均值，去除地表环境因素导致的温度差异影响，最后通过减去天池气象站当日的平均气温，去除气象因素的影响，得到了由火山活动引起的温度异常；4.从地震目录以及GPS基准站位移时间序列资料分析长白山天池火山2002‐2006年岩浆扰动事件的机理：2002年以来，太平洋板块俯冲速度有所加快，在日本岛弧地区表现为强震频发，而我国东北地区5级以上中强地震活动也明显增多，是板块俯冲加速导致应力调整在地表的体现。在此应力背景下，长白山天池火山的地幔岩浆房受到较大的应力触发，使得地壳岩浆房与地幔岩浆房的通道打开，引发一次小规模的岩浆补给，造成基性岩浆与酸性岩浆的混染，即触发岩浆扰动事件；5.利用InSAR技术研究长周期休眠火山的岩浆系统存储、运移机制：位于俄罗斯勘察加半岛的Kizimen火山历史上仅喷发过一次，是典型的监测能力较低的长周期休眠火山。本文基于ENVISAT ASAR（C波段）和ALOS PALSAR（L波段）两种影像资料（共6个航迹），共得到16个相干性较好的干涉图，结果显示Kizimen火山在2010年喷发前约两年开始发生大范围的地表隆升。形变场在升、降轨道的干涉图上表现迥异，本文采用升、降轨道干涉图联合反演，约束获得了岩浆源的几何参数。根据16幅干涉图得到的体积变化，本文利用加权最小二乘方法计算了体积变化时间序列。最后，结合火山地震目录资料，还原了喷发触发机制。通过以上研究，获得以下结论与认识：1.相对于华北华南块体，我国东北地区现今地壳水平运动比较活跃，整体趋势性明显；相对于长春基岩点，我国东北地区整体表现为西升东降的差异性垂直运动形变特征。在长期地壳垂直形变意义上，长白山天池火山并无明显的形变异常；2.长白山天池火山的岩浆房位于天池下方西北侧，深度约9km，与层析成像等地球物理监测资料一致。另外，由于岩浆上涌触发天池火山区分布的部分断裂两侧活动差异性明显；3.长白山天池火山的卫星热红外遥感监测结果表明，2002‐2006年火山活动产生的温度热异常逐年升高，每年上升约3‐7°C；到2005年，热异常达到了27.5°C，比2002年高出约10°C；自2005年开始，温度热异常明显下降，2006年下降了近10°C，以后温度场保持平稳的趋势，恢复到2002年以前的正常水平。与其他常规监测手段（测震、地表形变、流体地球化学）的趋势一致。由岩石变形与温度变化的弹性热力学关系，本文认为长白山天池火山地区在2002‐2006年发生了明显的岩浆扰动事件，导致岩浆房以及周围围岩受压，引起大范围的异常升温现象；4.长白山天池火山2002‐2006年的岩浆扰动事件，与同时间段内我国东北地区频发的5级以上中强深、浅源地震一样，都是太平洋板块向欧亚大陆下方加速俯冲造成的区域应力场变化的结果，而非2002年吉林汪清mb7.2深源地震触发；5.Kizimen火山的2010年喷发属于典型的裂隙侵入式喷发模式。喷发前，岩浆从深处上侵到7‐18km深处并开始累积存储，侵入始于2008年9月到2009年4月的某个时间。区域应力场的逐渐增加促进了Kizimen火山下方裂隙的拉张破裂，使得上侵的岩浆在裂隙内存储而形成狭长的存储区。裂隙破裂的开始阶段，伴随着区域内零星的地震活动，地表表现为微小的形变，随着岩浆的不断补给，裂隙的逐渐破裂，区域地震活动增加，表现为小震震群活动，以及地表的大范围较大形变。2010年1月前后，裂隙破裂向上传递接近地表，小震震群活动表现为震源深度逐渐变浅。逐渐补给的岩浆使得裂隙内的压力逐渐增大，最终超过了围岩的强度，岩浆从地壳最薄弱处冲出地表，形成了2010年11月中旬的喷发事件。总之，本文的研究明确了长白山天池火山的现今形变背景，确定了长白山天池火山下方的岩浆房的空间位置，建立了基于高空间分辨率遥感影像的卫星热红外遥感技术监测火山热异常的技术体系，探讨了长白山天池火山2002‐2006年岩浆扰动事件的机理，并研究了利用InSAR技术推断确定火山岩浆系统的存储、供给与运移动力机制的方法。更多还原

【Abstract】 The Changbaishan Tianchi volcano, located on the boundary of China and North Korea, is a stratovolcano which has potential eruption possibility. It made many explosive eruption events in history. The catastrophic eruption event that occurred946years ago is throught to be one of the most explosive events during the past2000years. In terms of the high risk of eruptive hazard, several ground‐based monitoring methods (e.g. deformation, seismology, and geochemistry) were used to detect the possible anomalies. However, the magma plumbing system and location of the magma chamber are unclear because those ground‐based methods are confined by the position and land cover of the Tianchi volcano. Also, parameters of the magma chamber from distinct models are different due to the sparseness of GPS sites, benchmarks. Moreover, all those conventional methods showed an obvious magmatic disturbance event occurred during2002‐2006, and the reason is unclear. Furthermore, study on the magma plumbing system is unsubstantial because China is lack of on‐going eruptive volcanoes. InSAR (Interferometric Synthetic Aperture Radar) has matured to become a widely used geodetic technique for measuring deformation of the Earth’s surface during the past two decades. InSAR can achieve a high spatio‐temporal sampling deformation field. Meanwhile, satellite thermal infrared remote sensing technology is proved to be a powerful tool, which can give the thermal anomalies of various land covers. Taking the Changbaishan Tianchi volcano as an example, this thesis finished several studies on volcano applications based on the two technologies. The research contents are as follows,1. Deformation background of the Changbaishan Tianchi volcano: Firstly, I gathered the GPS horizontal velocity fields of NE China, North China, South China, and the Japan area. Then, I gathered two periods of the first order leveling measurement results. At last, the vertical deformation field was achieved through an entire network adjustment method.2. Time series deformation of the Changbaishan Tianchi volcano based on PSInSAR: A time series deformation field (2004‐2010) was achieved by using PSInSAR technology based on18ENVISAT ASAR images. The results are consistent with the leveling measurements from the same period, which indicates that PSInSAR can detect slow deformation with high accuracy. Then, I modeled one of the accumulative deformation interferograms based on Mogi point source accounting for topography relief, and got the parameters of the magma chamber.3. Thermal anomalies of the Changbaishan Tianchi volcano: I established the system detecting the thermal anomalies in the volcanic area. Firstly, the land surface temperature was inversed through the Landsat TM/ETM or ASTER images, based on mono‐window algorithom, and temperature/emissivity separation algorithom, respectively. Then, the average temperatures of three different surface cover types were calculated. This removed the surface terrain effect on the temperature that inversed. At last, the average meterorological temperatures obtained from the Tianchi Meteorological station are substracted from the average temperatures of each type. Thus, the meteorological factor was removed. After this process, the remaining temperature is very likely the thermal anomaly caused by magmatic activity.4. The possible mechanism of the magmatic disturbance event that occurred during2002‐2006in the Changbaishan Tianchi Volcano: From2002, the Pacific slab subducted faster than it did before, which was indicated by strong earthquake swarm around the Japan island arc. At the same time, the number of strong earthquakes (Ms>=5) increased in Northeast China, which indicates a stress adjustment due to the subduction accelerating. So the conduit between crustal chamber and mantle chamber opened, which was triggered by the stress change. And then, the magma intrusion event occurred.5. Study on the magma plumbing system by InSAR: The Kizimen volcano, located on the Kamcahtka peninsula, Russia, is a typical long‐term dormant volcano. I used ENVISAT ASAR (C band) and ALOS PALSAR (L band) to create16interferograms with reasonable good coherence. The interferograms show that the deformation around the Kizimen volcano occurred about two years before the onset of the eruption. I jointly modeled two interferograms from ascending and descending tracks due to the different fringe patterns. At last, the time series volume changes were achieved by a weighted least square adjustment method. The magma plumbing mechanism was discussed based on the volume changes and earthquake catalogue.Conclusions are as follows based on the above studies.1. All the GPS horizontal velocities of NE China show a NW movement, with a rate of5mm/y, relative to North and South China blocks. The leveling results show that western part of NE China moves up while eastern part of NE China goes down, relative to the Changchun benchmark. The Changbaishan Tianchi volcano area does not show vertical deformation anomalies for a long term view.2. The Mogi point source modeling result shows that the magma chamber of the Changbaishan Tianchi volcano is located at the northwestern part of the Tianchi lake, with depth of9km. This result is consistent with the geophysical measurements. Moreover, the active faults also show obvious deformation due to the magma intrusion.3. The thermal infrared remote sensing results show apparent thermal anomalies in the Changbaishan Tianchi volcano during2002‐2006. From2002to2006, the thermal anomalies steadily increased with an annual increment about3‐7°C, and reached the peak of27.5°C in2005, which was about10°C higher than that in2002. As the turn point in2006till2008, the temperature of thermal anomalies suddenly dropped by about10°C back to the normal level as that in2002. The thermal anomalies are consistent with the gound‐based measurements. The thermal anomalies were caused by magma intrusion event, which leads to an intensive stress on magma chamber and countryrock.4. Based on the earthquake catalogue and deformation time series of GPS stations, I draw a conclusion that the magmatic disturbance event was caused by the subduction accelerating of the Pacific slab. The location of Wangqing deep earthquake (mb7.2) is too far to trigger the magmatic disturbance enent.5. The Kizimen eruption event that occurred in2010was a typical dike‐intrusion case. I infer that magma migrated from a deep source region into a storage zone perhaps7‐18km BSL beneath Kizimen sometime between September2008and April2009. The regional stress field favors the formation of dikes beneath the volcano, and as a result the intruding magma accumulated in an elongate, dike‐like storage zone. The zone dilated progressively over time, accompanied by sporadic earthquakes and subtle surface deformation. Continuing intrusions caused the intruded zone to widen, causing more surface deformation and increasing seismicity. Around January2010, a dike propagated upward to within a kilometer or so of the surface, as evidenced by sudden shoaling of earthquakes. Eventually, increasing magma pressure in the growing intrusion exceeded the confining strength of the host rock and magma breached the surface at the weakest part of the system, triggering the mid‐November2010eruption at Kizimen.In a word, after establishing the deformation background of the Changbaishan Tianchi volcano, this thesis confirmed the location of magma chamber. Moreover, this thesis established the volcano monitoring system based on satellite infrared remote sensing technology. It also discussed mechanism of the magma intrusion event that occurred in the Changbaishan Tianchi volcano during2002‐2006. Finally, it showed an example how to study the magma plumbing system by using InSAR.更多还原