Co-seismic and co-diking crustal deformation along subaerial rift zones detected by satellite synthetic aperture radar : East Africa, Iceland, and Southwestern Japan

• Main Author: 姫松, 裕志
• Other Authors: 古屋, 正人, 日置, 幸介, 村上, 亮, 高田, 陽一郎
• Format: Other/Unknown Material
• Language: English
• Published: Hokkaido University
• Subjects: 400; Iceland
• Online Access: http://hdl.handle.net/2115/76432; https://doi.org/10.14943/doctoral.k13574

Crustal deformation along the plate boundaries is one of the important research interests for elucidating their mechanisms because earthquake activities and volcanic eruptions usually concentrate along plate boundaries due to high strain rates. Along the divergent plate boundaries which usually call rift zone, we can observe the processes of continental rifting evolution, such as generating new crust and splitting continental crust. Most of the divergent plate boundaries, however, are located beneath the sea, and the onshore rift zones are only less than 2 % of all the rift zones on the Earth. The accumulation of crustal deformation data along the subaerial rift zones improves our understanding of the rift systems and the geophysical phenomena. The aim of this thesis is to reveal detailed crustal deformation along the subaerial rift zones by processing satellite SAR data, one of the space-based geodetic methods. SAR data can detect surface movement with high spatial resolution without installing on-site observation instruments, like GNSS receivers. This thesis focuses on three dike intrusion episodes and one earthquake event along the subaerial rift zones: 1) the 2007 Natron dike intrusion episode, Tanzania, 2) the 2005-2010 Afar dike intrusion episode, Ethiopia, 3) the 2014-2015 Bárðarbunga dike intrusion episode, Iceland, 4) the 2016 Kumamoto earthquake sequence, Japan. By applying InSAR and pixel tracking approaches to PALSAR-1 data the horizontal displacements parallel to the rift axis on the graben subsidence were detected during the 2007 Natron and the 2005-2010 Afar dike intrusion episodes which occurred along the East African Rift. The focal mechanisms during each episode indicate normal faulting with few strike-slip components, these strikes nearly coincide with the rift axis direction. Our inversion model confirmed that the optimal elastic models need not only normal faulting but also strike-slip components to reproduce the horizontal displacement on the graben subsidence. Thus the along-rift ...