CRUSTAL DYNAMICS RESEARCH WITH ALOS INTERFEROMETRY
| Autor: | Sandwell, David, Fialko, Yuri, Mellors, Rob, Wei, Meng, Tong, Xiaopeng |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2011 |
| Zdroj: | 宇宙航空研究開発機構特別資料 = JAXA Special Publication: Final Reports of the ALOS Research Announcement Programs 1&2, 2011. :PI114-PI114-11 |
| ISSN: | 1349-113X |
| Popis: | ALOS PALSAR is the first interferometric SAR mission with the ability to globally image (including vegetated areas) crustal deformation associated with earthquakes and volcanoes. We call it the "earthquake machine" because the instrument, spacecraft, and mission managers have captured the deformation signals of all major events since the satellite was launched in 2006. Our investigation using ALOS PALSAR had two main components. First we developed algorithms and software to exploit the new modes of operation. We were perhaps the first group, outside of Japan, to: (1) create an interferogram with FBS to FBS L1.0 data; (2) create mixed-mode FBD to FBS interferograms; (3) interpolate the state vectors to verify better than 10 cm orbital accuracy; (4) show the phase noise (in mm) for PALSAR is only 1.6 times worse than the phase noise at C-band even though the wavelength is 4 times longer; (5) demonstrate the expected improved temporal correlation properties of L-band with respect to C-band; and (6) develop the ability to create ScanSAR to ScanSAR interferograms as well as ScanSAR to FBDmode interferograms. We also discovered, as did our Japanese colleagues, that ionospheric waves with 20-40 km wavelength cause phase distortions as large as 20 cm that add significant noise to interferograms. We were unable to correct these phase distortions using GPS-derived ionospheric models because they have insufficient spatial resolution to capture even the 40-km length scales. Since our algorithms, software, and funding (NASA and NSF) are independent of JAXA, our group provides an independent check of the strengths and weaknesses of ALOS-PALSAR. The second main aspect of our investigation was to use these new InSAR data to image crustal deformation associated with: volcanic inflation at Kilauea, Hawaii; the major deformation and decorrelation from the M7.9 Wenchuan, China earthquake; the widespread deformation from the M8.8 Maule, Chile earthquake; and most recently the deformation and liquefaction from the M7.2 El Major-Cucapah earthquake just south of the US-Mexico border in the Mexicali valley. We have been less successful at using stacks of ALOS interferograms to image the interseismic crustal deformation along the San Andreas Fault system (SAF's). The typical spacing of continuously-operating GPS-receivers surrounding this fault system is 10 km so any new information from interferometry must capture deformation at smaller scales. We expect the amplitudes of these short-wavelength signals to be 1 to 5 mm/yr. There are two reasons why ALOS has not adequately captured these signals. First the interferometric baseline of ALOS drifts by 5 km over a 1.9 year timescale so we are only now beginning to have short spatial baseline and long temporal baseline pairs needed to image the mm-scale deformation rates. Second, ALOS has not collected much PALSAR data on descending (daytime) tracks that have the optimal geometry for observing strike-slip motion of the SAF's. As the ALOS mission moves into its 6 year of data collection, the number of long temporal baseline interferograms is rapidly increasing and we expect significant interseismic findings over the next few years. During our investigation we have participated in 8 ALOS PI meetings and have presented our results at 3 IGARSS meetings, 3 AGU meetings, 5 SCEC meetings, 3 EarthScope meetings and at least 6 invited talks at USC, Ohio State, Kyoto-DPRI, Stanford, UCSB, and UCR. Our group has published 8 papers in refereed journals. The remainder of this report describes the main findings from these publications. One of the most important aspects of the scientific use of ALOS PALSAR data is open access to large quantities. We are grateful to JAXA for supplying 50 scenes/yr from the AUIG site for our cal/val investigation. We were also allocated 50 scenes/year from the ASF AADN. However, these 50 scene allocations are insufficient for this type of crustal deformation research since each study discussed below required the analysis of between 50 and 200 scenes. The bulk of these data were obtained from the ASF DAAC through the L1 data pool that was supported with funds from NASA, NSF, and USGS. Moving data from JAXA to the AADN to the DAAC and finally into the L1-pool is sometimes slow and error prone so having access to the 50 scenes/yr at the AUIG site was a tremendous asset. The AUIG site contains all the PALSAR data and it is usually available, with precise orbits, within 2 days after acquisition. 形態: カラー図版あり 形態: DVD-ROM1枚 Physical characteristics: Original contains color illustrations Note: One DVD-ROM 資料番号: AA0065135012 レポート番号: JAXA-SP-11-007E |
| Databáze: | OpenAIRE |
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