The M w 7.9, 12 May 2008 Sichuan earthquake rupture measured by sub-pixel correlation of ALOS PALSAR amplitude images

Abstract

PALSAR L-band spaceborne Synthetic Aperture Radar (SAR) amplitude images are used to map the Sichuan earthquake rupture (China, M w 7.9, 12 May 2008) and to identify the faults activated by the earthquake. A sub-pixel correlation method is used to retrieve the coseismic displacement field projected into the line of sight of the satellite and the horizontal along-track direction, and to map the surface rupture. The earthquake broke ∼270 km of the Beichuan fault and ∼70 km of the Guanxian fault, with a complex thrust-dextral slip mechanism. Along the southwestern part of the rupture, slip seems to be partitioned into a dextral-dominant component on the Beichuan fault and a thrust-dominant component on the Guanxian fault. Dextral slip may also be dominant at the northeastern tip of the Beichuan ruptured fault. Coseismic surface displacements reach on average 3 to 4 m in both measured directions. The SAR rupture mapping has proven complementary to field studies extending the zone of co-seismic displacements and identifying other possible co-seismic rupture strands.

Recent Trend and Advance of Synthetic Aperture Radar with Selected Topics

“…In addition to azimuth streaks, ionospheric delays caused by the variations of total electron content (TEC) introduce Faraday rotation (see the polarization paragraphs in Section 1 and references therein), relative range delay between interferometric data acquisition times, range and azimuth defocusing, loss of interferometric coherence, and phase errors. Azimuth streaks and range shifts cause misregistration in the subpixel correlation in both the azimuth and range directions in interferometry, and decorrelation as reported in the study on the 2008 Sichuan Earthquake [635]. Due to the dispersive nature, the effects of ionospheric delays can, in principle, be separated from non-dispersive features of surface deformation and atmosphere.…”

“…The effects of ionospheric delays become significant at lower frequencies, since the variance of the refractive index fluctuations is approximately proportional to λ 4 , as observed in the RADARSAT C-band and JERS-1 L-band SAR amplitude images over the auroral zones in Alaska, showing kilometer-scale linear or banding patterns in the azimuth direction, termed as "azimuth streaks" [632]. The effects of ionospheric fluctuation have been observed near the magnetic poles [632,633], particularly during strong magnetic disturbances, but also in the areas away from the polar regions, such as the ALOS-PALSAR L-band data over Japan and Brazil [634], and the 2008 Sichuan Earthquake [635,636]. In addition to azimuth streaks, ionospheric delays caused by the variations of total electron content (TEC) introduce Faraday rotation (see the polarization paragraphs in Section 1 and references therein), relative range delay between interferometric data acquisition times, range and azimuth defocusing, loss of interferometric coherence, and phase errors.…”

“…Improved versions [635,636] have been proposed based on the relation between the ionospheric contributions to the azimuth offset and interferometric phase derived by Mayer et al [640,641]. From this relation the interferometric phase errors caused by the spatial variation of TEC, i.e., azimuth streaks, can be estimated empirically using the azimuth offset values [639] and removed, enhancing surface topography and coseismic deformation measures.…”

Coseismic and Postseismic Displacement of 2011 Mw 6.8 Tarlay Earthquake, Myanmar using InSAR Techniques and Inversion Analysis

“…This leads to a number of recent earthquake studies in non-arid areas with ALOS PALSAR L-band images. The examples of applying ALOS PALSAR for coseismic deformation was the Mw=7.9, 12 May 2008 Wenchuan earthquake that struck the western Sichuan province (China) along the topographic escarpment between the Tibetan plateau and the Sichuan basin [10][11][12][13]. The results show strike-slip motion along 145 kilometers long Yingxiu-Beichuan fault and mainly thrust faulting along the sub-parallel, 105 kilometers long Beichuan-Qingchuan fault.…”

Fast building damage mapping using a single post-earthquake PolSAR image: a case study of the 2010 Yushu earthquake

“…After an earthquake, the collapsed building information should be acquired in a timely manner and can be used to guide the effective implementation of the emergency rescue, which is crucial for the reduction in casualties (Susaki 2015). Although optical remote sensing images are intuitive and easy to understand, they are directly restricted by sunlight, and optical remote sensors cannot image the earth under cloudy, rainy, foggy, and other inclement weather (Gamba et al 2007;de Michele et al 2010). Radar is not affected by weather and climate and can obtain images in bad weather and even at night, because of its strong penetrative power (Yamaguchi 2012;Balz and Liao 2010), so it has become a reliable remote sensing data source for acquiring the damage information of earthquake-stricken areas (Dell' Acqua and Polli 2011).…”