A 26ka Continuous Stratigraphic Record of Surface Rupturing Earthquakes in Drill Logs Across the Xiadian Fault,Hebei Province,China

This paper deals wiah a new method for identification of long-term slip behavior of a conceaiedfault in a plain area from tectono-stratigraphic and chronological data obtained by drilling.Chronological determination and lithological analysis and correlation of sediments in stratigraphic colunms of drills NO.1 and No.2 at Dongliuhe Village on the hanging and foot walls ofXiadian fault allow us to quantitatively reconstruct the differential sedimentary history and vertical dislocation process on the hanging and foot walls of the fault since 26 ka BP and to set upa tectono-stratigraphic indicators for identifying paleoearthquakes.On this basis,taking theaccumulative vertical displacement of both sides of a fault to be a quantitative constraint,thestate before an abrupt dislocation in surface-rupturing earthquake can be reconstructed(de-ducting the later coseismic vertical displacement),then 11 surface-rupturing paleoseismic even-ts can be identified.A close correlation between recurrence behavior of

This paper deals with a new method for identification of long-term slip behavior of a concealed fault in a plain area from tectono-stratigraphic and chronological data obtained by drilling. Chronological determination and lithological analysis and correlation of sediments in strati-graphic columns of drills No. 1 and No. 2 at Dongliuhe Village on the hanging and foot walls of Xiadian fault allow us to quantitatively reconstruct the differential sedimentary history and vertical dislocation process on the hanging and foot walls of the fault since 26 ka BP and to set up a tectono-stratigraphic indicators for identifying paleoearthquakes. On this basis, taking the accumulative vertical displacement of both sides of a fault to be a quantitative constraint, the state before an abrupt dislocation in surface-rupturing earthquake can be reconstructed (deducting the later coseismic vertical displacement), then 11 surface-rupturing paleoseismic events can be identified. A close correlation between recurrence behavior of surface-rupturing paleoearthquakes on the Xiadian fault and paleoclimatic environment is found. Totally 6 surface-rupturing paleoearthquakes occurred in the Last Interstadial and Last Glacial Maximum (19.3 - 26 ka BP), during which the surface-rupturing paleoearthquakes had clustered on the Xiadian fault, with a recurrence interval of 900-1 900 a and mostly only 900 - 1 200 a. Then during the late stage of the Last Glacial period to Post-glacial period, the surface-rupturing paleoearthquakes obey to a quasi-periodic recurrence model, with an obviously longer recurrence interval . The recurrence interval of the last 5 surface-rupturing paleoearthquakes, including the 1679 Sanhe-Pinggu M 8.0 earthquake, was in a range from 3 700 a to 5 800 a.