Search

We analyzed Sentinel-1A (S1A)/IW satellite descending data from multiple acquisitions to map coseismic and post-seismic deformation fields and invert the fault slip and afterslip models associated with the seismic moment magnitude (Mw)8.3 earthquake that occurred at Illapel, Chile, on September 16th, 2015. We generated one coseismic and four post-seismic interferograms to analyze temporal and spatial variations in the deformation field after the mainshock; we found that the coseismic deformation field has a semicircular shape and covers a 300-km long and 190-km wide area. The maximum displacement reaches ca. 1.33 m in the LOS subsidence direction, while post-seismic deformation derived from four interferograms with different time intervals is mainly distributed within a long narrow area approximately 65 km wide. Maximum displacement is ca. 8 cm, including two regions of line of sight (LOS) uplift and sinking. Major regions of deformation exhibit opposite directions to the mainshock just after the event, before reverting to consistency. We inverted the coseismic fault slip and afterslip models based on a shallow-dip single fault plane in a homogeneous elastic half space. Our inversion suggests that coseismic slip is mainly concentrated in a shallow region to the northwest of the source, and that rupture length along strike is close to 340 km, with a maximum slip of about 8.16 m to the trench. The estimated moment is 3.126 × 10 21 N m (Mw8.27), and the maximum rupture depth is 50 km. Inverted residual slip also shows just one region of slip in the shallow subsurface, which is shifted slightly to the south. In the early stage of deformation, the residual is along the down-dip direction, with a maximum value of ca. 32 cm, before turning into the up-dip direction, with a maximum value of ca. 23 cm. Finally, we present a preliminary analysis of these complex changes in space and time.

We carry out an integrated study on coseismic and post-seismic deformation caused by 2010 Yushu earthquake sequence, including both mainshock and aftershocks, by using multi-scene ENVISAT/ASAR data on two adjacent tracks. We map the extended deformation region to the west of mainshock and show the westward extension of seismogenic fault of mainshock. Based on our whole deformation field derived from mosaic interferograms, the total length of seismogenic fault reaches $${\sim }103\,\hbox {km}$$ longer than $${\sim }71\,\hbox {km}$$ suggested by the previous report. Several coseismic interferograms with different time baselines have similar deformation patterns, which indicate that the influence of aftershocks and post-seismic slip on coseismic deformation field is limited. Also, we observe a clear and separate deformation area, $${\sim }38\,\hbox {km}$$ to the west of the mainshock epicentre, with maximum displacement of $${\sim }9\,\hbox {cm}$$ . The localised deformation is composed of two patches with opposite motion directions, where an aftershock cluster with at least 47 events ( $${>}\hbox {Ms}\,3.0$$ ) occurred. We infer that this localised deformation is caused by aftershocks ruptured on a blind active fault. While a weak post-seismic deformation band along main rupture zone near mainshock epicentre is likely attributable to short-term afterslip.