Sub-pixel Offset Tracking Algorithm And Its Application To Detection The Co-seismic Deformation Of Real Earthquakes

Earthquake is a major disaster phenomenon which is dangerous to humanity production and life. It is very necessary to study earthquake. Observational data of earthquake surface rupture have important significance for the study of earthquake mechanics and structural properties of the earthquake fault area. Fault geometry and slip distribution is the key to decide seismic dynamic rupture process. We can make use of surface deformation displacement field to inverse fault slip distribution and study the structure and rupture state of the fault. At the same time, we can use it as a boundary condition to restrain the earthquake fault movement. Therefore, for research in both seismic dynamics and kinematics problem, obtaining coseismic displacement field is a vital scientific problem.Based on the existing sub-pixel offset tracking algorithms, we proposed a sub-pixel offset tracking algorithm to detect earthquakes coseismic displacement field, combined with the cross-correlation, bilinear interpolation and two-dimensional Gaussian regression. We wrote a program by C language to implement the algorithm and applied this algorithm to real earthquake. We computed coseismic deformation diplacement field of the February 14,2014 Yutian earthquake and September 24,2013 Pakistan earthquake. We applied masking processing, filtering processing, differential calculation and other post-processing to initinal displacement field to get accurate and smooth coseismic diplacement field.There are two left-lateral strike-slip fault on the east of 2014 Yutian earthquake epicenter. The rupture is mainly left-lateral strike-slip peaking to 1.5m and some normal slip component. The ruptere is about 20km and the strike of the fault is about N60° E. Results which we caculated are consistent with other researchers. On the south of the epicenter where is main distribution area of aftershocks, there is a nearly north-south arc-shaped rupture.The surface rupture of 2013 Pakistan earthquake is mainly left-lateral strike-slip, peaking to 10m and averaging to 6m. The slip on the northwest side of fault is significantly greater than the slip on the southeast side of fault. We provided the probable cause why the thrust fault occurs the strike-slip earthquake. The coseismic displacement field of Pakistan earthquake which we caculated is consistent with the results of other researchers. Precision pixel level can reach three percent. The results of the application in two real earthquakes illustrate the new developed sub-pixel offset tracking algorithm can calculate coseismic displacement field of moderate or strong earthquake effective.