| 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. |
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