11:15 〜 11:30
[J05-4-03] Observation of aseismic crustal deformation in Taiwan by analysis of InSAR and GPS data
In this study, we report aseismic crustal deformation detected by InSAR images and GPS data in southwestern Taiwan where is characterized by high convergence rate and very low seismicity. GPS observation network has been well established there, which is preferable to correct noisy interferograms. We use SAR data of L-band satellites (ALOS and ALOS-2) to obtain coherent images even for dense forests.
After removing long wave-length noise and height dependent term from interferograms using the GPS velocity field (Tsai et al, 2015) and DEM, we stacked the corrected interferograms for further noise reduction. Using these images, we derived the quasi-vertical and quasi-east velocity fields. We found very rapid uplift in the area stretching about 25 km in the N-S direction with about 5 km E-W width. The uplift rate increases from south to the north, and it shows step-wise change in the eastern flank. Ching et al, (2016) reported up to 20 mm/yr uplift rate detected by leveling survey passing through the southern part of the uplift area. The quasi-uplift rate obtained by InSAR at the southern part is consistent with those given by leveling survey. On the other hand, the maximum uplift rate detected by InSAR reaches up to 45 mm per year at the northern part, twice as large as the rate along the levelling route. Judging from very low seismicity in this region, the severe crustal deformation we detected with InSAR is aseismic.
The 2-D distribution of whole uplift rate seems impossible to explain only by fault motion, and mud diapir should be another important factor. We found a sharp displacement discontinuity in the coseismic interferogram of the Meinong earthquake (M6.4), which implies that the aseismic uplift is mainly driven by the mud diapir, but the shallow active fault works as a pre-existing weakness.
After removing long wave-length noise and height dependent term from interferograms using the GPS velocity field (Tsai et al, 2015) and DEM, we stacked the corrected interferograms for further noise reduction. Using these images, we derived the quasi-vertical and quasi-east velocity fields. We found very rapid uplift in the area stretching about 25 km in the N-S direction with about 5 km E-W width. The uplift rate increases from south to the north, and it shows step-wise change in the eastern flank. Ching et al, (2016) reported up to 20 mm/yr uplift rate detected by leveling survey passing through the southern part of the uplift area. The quasi-uplift rate obtained by InSAR at the southern part is consistent with those given by leveling survey. On the other hand, the maximum uplift rate detected by InSAR reaches up to 45 mm per year at the northern part, twice as large as the rate along the levelling route. Judging from very low seismicity in this region, the severe crustal deformation we detected with InSAR is aseismic.
The 2-D distribution of whole uplift rate seems impossible to explain only by fault motion, and mud diapir should be another important factor. We found a sharp displacement discontinuity in the coseismic interferogram of the Meinong earthquake (M6.4), which implies that the aseismic uplift is mainly driven by the mud diapir, but the shallow active fault works as a pre-existing weakness.