CAJ | 학술논문

汶川大地震中XI级烈度区内水井岩滑坡现场等地爆炸声、特大型滑坡现场巨大环形坑和远距离抛射碎石等记录和现象，需给出科学解释。在地震发生后多次现场地质调查和走访、样品采集和多项分析测试及其结果比较等基础上，对主中央断裂F2控制的下盘陈家坝水井岩大型滑坡体上环形坑周边不同距离范围内散落烧焦残留的硅酸盐和碳酸岩等采样后，开展了物质成分和微观结构分析。结果发现：与原生溶蚀灰岩、薄层煤岩结构和有机质成分不同，这些抛散在滑体表面的样品中富含经强烈高温作用的块石，一些成分以锰碳酸盐岩等为主的暗棕色样品中稠环芳烃是其经历过强烈热作用过程而使有机质发生环化芳构化反应的结果，即样品经过了强烈热降解作用，显示其形成时出现强烈热作用过程和高温裂解现象。结合本区地质构造特征和煤层气分布情况、地震后实施的汶川地震带深钻在穿越主中央断裂带F2深度处监测到余震过程中甲烷含量异常增高、东河口地震遗址公园发现温泉及天然气溢出等资料和研究结果，讨论了地震诱发的富含甲烷的天然气爆炸，其加剧或伴生着地震次生地质灾害。由此推测：与碳质岩或煤系共存的喀斯特溶洞中封闭煤层气在地震过程中突溢和爆炸燃烧，叠加或放大了地震作用，结果在滑坡堆积体表面残留了多处环形爆炸坑，引发了一些岩块大规模长距离水平抛撒等。研究结果对监测和认识发震断层带在地震过程中天然气爆炸诱发和加剧滑坡灾害有重要意义。
문천대지진중XI급열도구내수정암활파현장등지폭작성、특대형활파현장거대배형갱화원거리포사쇄석등기록화현상，수급출과학해석。재지진발생후다차현장지질조사화주방、양품채집화다항분석측시급기결과비교등기출상，대주중앙단렬F2공제적하반진가패수정암대형활파체상배형갱주변불동거리범위내산락소초잔류적규산염화탄산암등채양후，개전료물질성분화미관결구분석。결과발현：여원생용식회암、박층매암결구화유궤질성분불동，저사포산재활체표면적양품중부함경강렬고온작용적괴석，일사성분이맹탄산염암등위주적암종색양품중주배방경시기경력과강렬열작용과정이사유궤질발생배화방구화반응적결과，즉양품경과료강렬열강해작용，현시기형성시출현강렬열작용과정화고온렬해현상。결합본구지질구조특정화매층기분포정황、지진후실시적문천지진대심찬재천월주중앙단렬대F2심도처감측도여진과정중갑완함량이상증고、동하구지진유지공완발현온천급천연기일출등자료화연구결과，토론료지진유발적부함갑완적천연기폭작，기가극혹반생착지진차생지질재해。유차추측：여탄질암혹매계공존적객사특용동중봉폐매층기재지진과정중돌일화폭작연소，첩가혹방대료지진작용，결과재활파퇴적체표면잔류료다처배형폭작갱，인발료일사암괴대규모장거리수평포살등。연구결과대감측화인식발진단층대재지진과정중천연기폭작유발화가극활파재해유중요의의。
Scientific interpretations are required for some abnormal phenomena at the XI intensity region of the Wenchuan earthquake :explosion bangs ,large size circular pits and far distance flying rock avalanches .During field surveys we found circular pits and ejecta distributed above the Shuijingyan rock avalanche at Beichuan County in June 20 ,2008 ,about one month after the main shock .According to field investigation and lab test results ,the fired ejecta around craters are mainly carbonate manganese mixed of corrosion limestone and manganese underground surface .The brown porous ejecta are featured by intensive thermophilic degradation because they had high content of polycyclic aromatic hydrocarbons .If the regional geological conditions and coalbed gas distribution are considered ,together with some updated findings of abnormal high content of methane monitored at the depth of central active fault F2 during aftershocks ,it is inferred that the main shock induced gas explosion ,the latter triggered and enhanced some huge scale rock avalanches . The methane is stored within corrosion caves in limestone which interbedded with carbonaceous rocks ,and closed fissures near the F2 .At the lower wall the local explosions left circular pits and fired eject around the pits ,triggered and enhanced the following rock avalanches to fly far distances .The result presented is significant for monitoring the natural gas explosions in great shock and understanding its functions to large scale rock avalanches .