Slip Model And Co-seismic Displacement Field Derived From Near Source Strong Motion Records

The mechanisms of the preparation,occurrence and evolution of the earthquake have always been an important goal and one of the frontier topics in seismology research.The distribution characteristics of high precision co-seismic displacement field not only can reveal the damage range,degree,attenuation characteristics,source dislocation mechanism,the complexity of fault structuire and so on,but also can be used to invert the slip model,so as to describe the occurrence and evolution process of an earthquake in space.Finally,the slip model is used to further calculate the Coulomb stress changes and influence,so as to analyze the evolution trend of the seismogenic fault or adjacent faults after the earthquake.At present,the co-seismic displacement field is mainly obtained by space-to-ground measurement technology such as GPS and InSAR,because GPS and InSAR have high precision.But the results are unable to be quickly acquired or shared because of the complexity of the calculation methods and procedures,the high cost of data acquisition and the long calculation period.Therefore.GPS and InSAR are only used for post-earthquake scientific research,which is difficult to be applied to earthquake emergency response such as emergency rescue and disaster rapid assessment after 72 hours of earthquake.Most of the strong motion records achieve real-time or quasi-real-time transmission,and the strong motion seismograph itself and its installation,maintenance costs are low,so the data is relatively cheaper and easier to share.What is more important is that the method of resolving strong motion data has been automated,simple,convenient and fast.However,when the co-seismic displacement field is calculated by using strong motion data,due to environmental interference,instrument noise,near-fault surface tilt and rotation,there is obvious baseline shift in the displacement which accompanied with double integration of acceeration records,so effective baseline correction of strong motion records is required.In this paper,near-source co-seismic displacement of the 16 April 2016 Mw7.0 Kumamoto.Japan,and the 24 August 2016 Mw6.2 Perugja,Italy,earthquakes are estimated from near-source strong motion records ater correction for their baseline shift using improved empirical baseline correction scheme:SMBLOC,which proposed by Dr.Wangrongjiang worked in GFZ,and compared with GPS observations.Furthermore,using GPS and strong motion record to invert the slip model of these two earthquakes respectively and jointly.Finally according to the slip model,the full spatial co-seismic displacement field can be predicted.So the conclusions we have gottten are as follows:(1)The maximum horizontal co-seismic displacement of Kumamoto earthquake based on strong motion records and GPS observations close to 100cm,and all show that fault rupture is mainly right lateral strike-slip mechanism(also a few normal-fault dislocation).The maximum horizontal and vertical displacement occurred at the station KMMH16 and KMM005,about 104.5cm and 58.0cm,respectively.(2)The three slip models of the Kumamoto earthquake all show double-event characteristics that the large slip is mainly distributed on the northeastward of the epicenter(second event).The moment magnitude is estimated to be Mw7.1 and the peak slip of strong motion model is 5.10 m and GPS model is 5.87 m.(3)The strong motion and GPS horizontal displacement fields of Perugia earthquake magnitude are cm and all show that fault rupture is mainly normal fault mechanism,and a few strike-slip dislocation.The maximum horizontal and vertical displacement of strong motion records reached 3.9 cm and 5 cm,and occurred at the station AMT.(4)The two slip models of Perugia earthquake base on different kinds of data and method are roughly similar not only in range but also in maximum slip,which occurred in the northeast of the epicenter.The slip model derived from strong motion data shows obvious double-event characteristics that the large slip is mainly distributed on the northeast and southeast sides of the epicenter,while the slip model inverted from GPS is relatively small on the southeast side of the epicenter,so it was not obvious double-event characteristics.The peak slip of GPS and strong motion models is 0.86m and 0.96m respectively.The moment magnitude is both around Mw6.3.So under certain conditions,the SMBLOC method can be used to estimate the co-seismic displacement field for the earthquake of magnitude about Mw6.0 and invert the slip model using its nearly filed strong motion data.In this paper,we analyzed two inland earthquakes with different magnitude ranges and different source mechanisms.The large displacement area in two grid predicted displacement fields based on slip models,consistent with the serious disaster area in the post-earthquake report.It is shown that when the station is densely distributed and the distribution is relatively uniform,using near-source strong motion records to calculates co-seismic displacement rapidly and to invert slip model,which can provide reference for the post earthquake emergency response,such as the assessment of seismic hazard,the distribution of the rescue force and so on.