Detection of damaged urban areas using interferometric SAR coherence change with PALSAR-2

Abstract

The interferometric SAR coherence-change technique with coherence filter and polarization (HH and HV) has been used to detect the parts of buildings damaged by the 2015 Gorkha Earthquake. A survey of the building damage was conducted in every house to evaluate the detection accuracy in the Khokana and Sankhu urban areas in the Kathmandu Valley of Nepal. The damaged parts of the urban area were adequately detected using coherence-change (∆γ) values obtained before the earthquake (γ pre ) and during the inter-seismic stage of the earthquake (γ int ). The use of a coherence filter effectively increased overall accuracy by ~2.1 to 7.0 % with HH polarization. The incorporation of HV polarization marginally increased the accuracy (~0.9 to 1.2 %). It was confirmed that road damage due to liquefaction was also observed using the interferometric SAR coherence-change detection technique. The classification accuracy was lower (27.1-35.1 %) for areas that were damaged. However, higher accuracy (97.8-99.2 %) was achieved for areas that were damage-free, in ∆γ obtained from HH and HV polarization with a coherence filter. This helped to identify the damaged urban areas (using this technique) immediately after occurrence of an earthquake event.

Fusion of Multi-Temporal Interferometric Coherence and Optical Image Data for the 2016 Kumamoto Earthquake Damage Assessment

“…This study thus demonstrates that it is feasible to combine and extend the advantages of two different remote sensing sensors for earthquake damage assessments. The urban damage levels following the 2016 Kumamoto earthquake were obtained from the degree of interferometric coherence of pre-seismic and co-seismic data, and the findings were consistent with the results of previous research reports that mapped the urban damage [11][12][13]15] and liquefaction areas [27] by using interferometric coherence.…”

“…We evaluated buildings damaged by the earthquake [10][11][12] and detected areas of soil liquefaction [27]. The normalized difference (ND) of the coherence change (Equation (2)) was also used to detect damaged areas [9,13]:…”

“…Hoffmann [12] mapped earthquake damage by interferometric coherence change during the Bam (Iran) earthquake in 2003 and achieved reliable results. Interferometric coherence by ALOS-2 (Advanced Land Observing Satellite-2)/PALSAR-2 (Phased Array Type L-Band Synthetic Aperture Radar) has been used successfully to detect Nepal earthquake damage in 2015 [13][14][15]. Furthermore, combinations of SAR data and optical images increased the accuracy of the earthquake damage assessments that were conducted after the Izmit and Bam earthquakes [16].…”

Building Damage Assessment Using Multisensor Dual-Polarized Synthetic Aperture Radar Data for the 2016 M 6.2 Amatrice Earthquake, Italy

“…Then, three main components were quantitatively considered in the discriminant analysis: first, the revised absolute mean differential coherence (|c r |); secondly, the absolute mean differential intensity ( d ); and thirdly, the binary map derived from optical imagery. Because the main SAR scattering mechanism over the built-up areas is double-bounce scattering, the incorporation of SAR intensity and SAR coherence for VV and HH polarizations resulted in higher values at an orientation angle (ϕ) near 0 • ; moreover, the incorporation of SAR intensity and SAR coherence for VH and HV polarizations also resulted in higher values with ϕ ≥ 0 • [31][32][33]. By incorporating different polarizations, the effect of ϕ as an important parameter on both the building orientation and the power signature is taken into account.…”

Sensitivity and Limitation in Damage Detection for Individual Buildings Using InSAR Coherence—A Case Study in 2016 Kumamoto Earthquakes

“…The Japan Aerospace Exploration Agency (JAXA) operates ALOS-2 to observe various disasters. Analytical results in the 2015 Nepal Gorkha Earthquake using ALOS-2 with the 10-m resolution mode suggested that a single building can be detected by interferometric analysis [21,22]. However, the 10-m resolution was too rough compared with the scale of the building.…”