The Research On The New Activities Of The Yilan Section Of The Yilan-Yitong Fault Zone And Its Influence For The Surrounding Coal Resource

The Yilan-Yitong Fault Zone(YYFZ)is one of the key branches of northern section of the Tan Lu fault,and also be viewed as the largest sesimotectoic in NE China.Recently,the Tonghe Holocene active part was discovered with the potential of strong earthquake(M?7),which thoroughly changed the traditional viewpoint that the YYFZ is of weak activity or inactivity in late Quaternary.Accordingly,the potential earthquake source and magnitude in the fifth edition were modified greatly based on this new discovery.In this context,it would be very helpful for us to conduct the research on the new activities of the Yilan section of the YYFZ in the angle of science and practice,which would help us to know the seismic activity background of NE China more scientifically,and to give the suggestions of earthquake fortification about the Third Coal Mine(TCM)morereasonably.The paper chooses the new activity of the Yilan section of the YYFZ and its influence for the surrounding coals as the research object,and propose earthquake fortification parameters of the TCM as reasonable as possible based on the synthesized methods of pale seismology and geomorphology and geophysics.The geometric construction of the Yilan section of the YYFZ in plain consists of three main NE-SW-oriented faults.Among which,the western branch runs in accordance with the eastern branch,and the middle section mainly developed in the interior of the basin.It is suggested that the latest active time of the eastern and western branchesae earlier than late Pleistocene,while the middle section is belonging to active fault.Studies of fault kinematics show that reverse strike-slip deformation has dominated along the YYFZ since late Holocene.There is no need for the Yilan TCM to consider the avoiding distance because the eastern branch of the YYFZ is not belong to the active fault by definition and constructionlaw.However,the potential earthquake source of Fangzhen(M7.5)should be considered during the construction.Also,theearthquake engineering research is conduced further based on the related parameters of YYFZ in the paper.Bedrock horizontal ground motion peakacceleration value of site in the next 50 years with 10% probability ofexceedance is126.3gal,and the bedrock horizontal ground motion peak acceleration value of site in the next 100 years with 10% probability ofexceedance is 192.9gal.Engineering site soil shear wave velocity values are 253.0m/s,276.8m/s,and 253.2 m/s respectively,and the overburden thickness of which is 26 m,which hints that the site belong to second type according to current earthquake resistant design code(GB50011-2010).Simultaneously,18 pieces of artificial ground motion time history samples are given for the soil layers seismic response analysis.Surface horizontal ground motion peak acceleration value of site in the next 50 years with 10% probability ofexceedance is174.5gal,and the Surface horizontal ground motion peak acceleration value of site in the next 100 years with 10% probability ofexceedance is 284.3gal,accordingly.The characteristic period of surface design response spectrum in the next 50 years with10% probability ofexceedance is 0.5s,and the characteristic period of surface design response spectrum in the next 100 years with 10% probability ofexceedance is 0.55 s.In summary,many new discoveries about the geometric and kinematic features of the Yilan section of the YYFZ are revealed,which would enrich our knowledge about the new activities of the YYFZ,as well as the neotectonic deformation and potential seismicity of the YYFZ and its neighboring areas,espeicalyy for the Seismic fortification parameter design of coal field.