SAR interferometry using ALOS-2 PALSAR-2 data for the Mw 7.8 Gorkha, Nepal earthquake

Natsuaki, Ryo; Nagai, Hiroto; Motohka, Takeshi; Ohki, Masato; Thapa, Rajesh; Tadono, Takeo; Shimada, Masanobu; Suzuki, Shuichi

doi:10.1186/s40623-016-0394-4

Cited by 36 publications

(20 citation statements)

References 22 publications

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“…The most popular application of SAR for a disaster is to estimate crustal movement during earthquakes and volcanic activity. The wide range of crustal movement induced by the 2015 Gorkha Earthquake was quickly examined with PALSAR-2 (phased array type L-band synthetic aperture radar 2)/ScanSAR mode) (Natsuaki et al 2016;Kobayashi et al 2015). The effective detection of urban areas damaged in 2011 off the Pacific Coast of Tohoku by the earthquake-induced tsunami was demonstrated using full polarimetry data obtained with the Japanese L-band SAR satellite, PALSAR (Watanabe et al 2012).…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2016

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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.

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Section: Introductionmentioning

confidence: 99%

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

et al. 2016

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“…They counted the actual offset of two SLC images by cross-correlation co-registration and fitted it to a sine function. These two functions led to almost the same offsets, i.e., either of the functions can be used for offset prediction of the ScanSAR images acquired prior to 8 February 2015 [16].…”

Section: Alos-2 Scansar Modementioning

confidence: 80%

“…The misalignment pattern before 8 February 2015 has been investigated in [15,16] by comparing against the data acquired after the modification. However, the precise overlap ratio/misalignment after the modification have not been evaluated to date.…”

Section: Introductionmentioning

confidence: 99%

Burst Misalignment Evaluation for ALOS-2 PALSAR-2 ScanSAR-ScanSAR Interferometry

et al. 2017

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This paper reports the validation results of burst misalignment for ScanSAR-ScanSAR interferometry of the Phased Array-type L-band Synthetic Aperture Radar-2 (PALSAR-2) aboard the Advanced Land Observing Satellite-2 (ALOS-2, "DAICHI-2"). After the internal software modification on 8 February 2015, ALOS-2 ScanSAR observation mode archives have been available for use in interferometric analysis, as it was planned. However, it has not been reported whether its burst misalignment satisfies the mission requirements: 90% or higher burst overlap ratio. The validation results in this paper confirm that the expected observation misalignment satisfies the required range, including minimal seasonal and orbital dependencies. The results in this paper are obtained directly from the azimuth offset of the single look complex (SLC) data and are not derived from the orbit records. Nine identical orbits and frame numbers are chosen and evaluated to investigate the average burst misalignment and orbital dependency.

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“…To validate whether observed signals were due to propagation delay in the troposphere or not, we generated other ScanSAR interferograms acquired at different times. It is noted that ALOS-2 ScanSAR interferometry with SLCs acquired before February 8, 2015, has "the burst overlapping" problem due to the incorrect parameter estimation of the satellite latitude, which causes the misalignment of the radio wave transmission timing (Natsuaki et al 2016). The successful interferogram generation requires the burst overlapping ratio of at least 50% (Buckley and Gudipati 2011).…”

Section: Insar Observationsmentioning

confidence: 99%

Detections and simulations of tropospheric water vapor fluctuations due to trapped lee waves by ALOS-2/PALSAR-2 ScanSAR interferometry

Kinoshita

Morishita

Hirabayashi

2017

Earth Planets Space

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Detailed wave-like spatial patterns of atmospheric propagation delay signals associated with mountain lee waves were detected in Hokkaido and Tohoku by synthetic aperture radar (SAR) interferometry (InSAR) with the ScanSAR mode observation data of a Phased Array-type L-band Synthetic Aperture Radar 2 on board the Advanced Land Observing Satellite 2. Both cases occurred under stable atmosphere conditions. The InSAR-observed peak-to-trough line of sight changes in the mountain wave signals was 4 and 5 cm with the horizontal wavelengths of 9 and 15 km in Hokkaido and Tohoku, respectively. Locations of positive phase maxima in the mountain wave signals coincides with locations of cloud streets observed by visible satellite imagery, indicating that crests of mountain waves contain relatively much water vapor compared with wave troughs. Numerical weather simulations with the horizontal grid spacing of 1 km were performed to reproduce InSAR phase variations, and as a result those simulations could reasonably reproduce observed wave amplitudes and wavelengths in both cases. On the other hand, numerical simulations tended to overestimate wave attenuation rates: simulated mountain waves decreased as the wave propagated faster than those of observed signals. Because the simulated wave attenuation rate is sensitive to physics in the planetary boundary layer (PBL), we investigated the reproducibility of five PBL schemes implemented in the WRF model. As a result, all the PBL schemes showed little attenuation except for the Yonsei University scheme (YSU), while the wavelength in the YSU was most close to the observation. Our study demonstrated the uniqueness and usefulness of InSAR for meteorological application as the ability to map the detailed water vapor distribution regardless of cloud cover. In addition, the reasonable reproducibility of the water vapor delay signal due to lee waves by the numerical weather model encourages researchers who tackle the correction of the tropospheric propagation delay, increasing the accuracy in detecting surface deformations.

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SAR interferometry using ALOS-2 PALSAR-2 data for the Mw 7.8 Gorkha, Nepal earthquake

Cited by 36 publications

References 22 publications

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

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

Burst Misalignment Evaluation for ALOS-2 PALSAR-2 ScanSAR-ScanSAR Interferometry

Detections and simulations of tropospheric water vapor fluctuations due to trapped lee waves by ALOS-2/PALSAR-2 ScanSAR interferometry

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