CAJ | 학술논문

通过地震调查、土工试验和14C测年，从沂沭断裂地震带安丘地区的全新世中—晚期湖沼相软土中，识别出了软土震陷灾害现象和地震产生的软土沉陷向斜褶曲、小尺度同震断层、狭缩–膨胀构造和震裂缝等共生土层变形构造，其中，软土沉陷向斜是直接反应震陷灾害的纵向土层变形。小尺度同震断层是地震产生的小断层，发育在沉陷向斜之下，其垂向延长0.5～1.8 m。沉陷向斜随着同震断层的产生而初现；又紧随断层向深部延伸而向下发展。地震振动使饱和软土发生触变，土质点从沉陷向斜的转折端向两翼发生流动，在此过程中，附加地震应力不断作用，结果形成了窄而深的沉陷向斜。软土震陷最大深度为1.08 m，平均震陷深度为0.68 m。推断当时的地震烈度达到Ⅷ度、震级超过M6。测得淤泥质土的14C年龄为3901±33a B.P.，该地震事件约发生公元前19世纪。同震断层是形成震陷的重要诱导因素，这为认识软土震陷的形成机理提供了新资料；也为防治或减轻软土震陷的危害提出了新启示。因此，应重视软土下伏土层可能产生同震断层的隐患。
통과지진조사、토공시험화14C측년，종기술단렬지진대안구지구적전신세중—만기호소상연토중，식별출료연토진함재해현상화지진산생적연토침함향사습곡、소척도동진단층、협축–팽창구조화진렬봉등공생토층변형구조，기중，연토침함향사시직접반응진함재해적종향토층변형。소척도동진단층시지진산생적소단층，발육재침함향사지하，기수향연장0.5～1.8 m。침함향사수착동진단층적산생이초현；우긴수단층향심부연신이향하발전。지진진동사포화연토발생촉변，토질점종침함향사적전절단향량익발생류동，재차과정중，부가지진응력불단작용，결과형성료착이심적침함향사。연토진함최대심도위1.08 m，평균진함심도위0.68 m。추단당시적지진열도체도Ⅷ도、진급초과M6。측득어니질토적14C년령위3901±33a B.P.，해지진사건약발생공원전19세기。동진단층시형성진함적중요유도인소，저위인식연토진함적형성궤리제공료신자료；야위방치혹감경연토진함적위해제출료신계시。인차，응중시연토하복토층가능산생동진단층적은환。
By means of seism investigation, soil test and14C dating, disaster phenomena about seismic subsidence of soft soils and some earthquake-induced association structures of soil layers are identified in soft soils of limnetic facies during the Mid-late Holocene in the Anqiu area of Yishu fault-seismic zone, including subsidence synform folds of soft soils, small scale co-seismic faults, pinch-and-swell structures and seismic fissures, in which subsidence synforms are vertical deformations that directly reflect the seismic subsidence disaster. Small scale co-seismic faults are some little faults caused by earthquakes, with vertical lengths of 0.5~1.8 munder the subsidence synform. A subsidence synform comes at first along with producing of co-seismic faults and developes downward treading on the heels of these faults extending to the even deeper place. The earthquake vibration causes the thixotropic deformation of saturated soft soils, and soil particles flow from the hinge zone to two wings of the synform, in which the seismic additional stresses act continually, resulting in formation of the narrow and deep-seated subsidence synform. The deepest seismic subsidence of soft soils is 1.08 m, and the average depth is 0.68 m. It is estimated that the seismic intensity is VIII degree, and the earthquake magnitude is over M6.0. The formation age of the mucky soils for 3901±33a B.P. is obtained by the14C dating, so the seismic event occurred in about 19th Century B.C.. The co-seismic fault is an important factor for forming the seismic subsidence of soft soils, which provides the new information for understanding the formation mechanism of the seismic subsidence of soft soils and the new revelation for preventing or mitigating the harm of the seismic subsidence. Therefore, attention should be paid to possible hidden troubles of co-seismic faults to be produced in the underlying layer of soft soils.