Burst mode to strip-map mode SAR interferometry of ALOS PALSAR

A complete processing flow is proposed to implement burst mode to strip-map mode interferometry for ALOS PALSAR data. The processing flow is applied to an interferometric pair comprised of FBD (High Resolution mode [Dual polarization], belonging to strip-map mode) and WB1 (Wide observation mode, belonging to burst mode) mode of PALSAR. Interferometric products including differential interferometric phase and DEM are generated. The evaluation of these products shows satisfactory precision.Geosciences, MultidisciplinaryRemote SensingCPCI-S(ISTP)

Widespread initiation, reactivation, and acceleration of landslides in the northern California Coast Ranges due to extreme rainfall

Episodically to continuously active slow‐moving landslides are driven by precipitation. Climate change, which is altering both the frequency and magnitude of precipitation worldwide, is therefore predicted to have a major impact on landslides. Here we examine the behavior of hundreds of slow‐moving landslides in northern California in response to large changes in annual precipitation that occurred between 2016 and 2018. We quantify the landslide displacement using repeat‐pass radar interferometry and pixel offset tracking techniques on a novel dataset from the airborne NASA/JPL Uninhabited Aerial Vehicle Synthetic Aperture Radar. We found that 312 landslides were moving due to extreme rainfall during 2017, compared to 119 during 2016, which was the final year of a historic multi‐year drought. However, with a return to below‐average rainfall in 2018, only 146 landslides remained in motion. The increased number of landslides during 2017 was primarily accommodated by landslides that were smaller than the landslides that remained active between 2016 and 2018. Furthermore, by examining a subset of 51 landslides, we found that 49 had increased velocities during 2017 when compared to 2016. Our results show that slow‐moving landslides are sensitive to large changes in annual precipitation, particularly the smaller and thinner landslides that likely experience larger basal pore‐water pressure changes. Based on climate model predictions for the next century in California, which include increases in average annual precipitation and increases in the frequency of dry‐to‐wet extremes, we hypothesize that there will be an overall increase in landslide activity

Multi-mode SAR Interferometry Processing Research and Implementation

Current operation mode of SAR can be roughly divided into two types: strip-map mode and burst mode. The most conventional mode is strip-map mode, in which the swath width is quite limited. The other type is burst mode, which is an active option to overcome this limitation by cyclically scanning several subswaths, known as ScanSAR. In addition, Envisat ASAR has another type of burst mode, that is, Alternating Polarization mode. ALOS PALSAR and Radarsat-1 also have their own ScanSAR operation modes, but each of them is distinctive from the others in implementation. Numerous theoretical results and applications of interferometry using strip-map data have been published before. Interferometry with burst mode data, however, is much rarer and different from the case of the traditional strip-map mode from raw data focusing to interferogram generation because of its burst nature of data acquisition pattern. In our study, we put our emphasis on each kind of burst mode interferometry and mixed mode interferometry. Until now, our successful research work includes Envisat ASAR WS-WS, IM-WS and ALOS PALSAR WB1-WB1 Interferometry. Other development activities including Envisat AP-AP and Radarsat-1 SNA-SNA interferometry are still on going. In the following paper, we will present our results and give an overview of multi-mode SAR. interferometry for the present spaceborne SAR sensors.Engineering, Electrical & ElectronicPhysics, AppliedEICPCI-S(ISTP)

Source parameters of the 2017 M_w 6.2 Yukon earthquake doublet inferred from coseismic GPS and ALOS-2 deformation measurements

We investigated an M_w ∼ 6.2 earthquake doublet on the border of the USA and Canada using ALOS2 Light-of-Sight displacements and GPS measurements. We selected three L-band ALOS-2 interfergorams with temporal baselines of one yr to extract coseismic deformation maps, in which master and slave images were both acquired in July. A subpixel-based alignment and another range spectral splitting techniques under the GAMMA InSAR software framework were applied to improve the interferometric coherence and reduce the effects of phase anomalies in two of the three interferometric pairs due to either ionospheric delay or a potential focusing issues in the generation of the ALOS2 SLC data. The updated interferograms convincingly reveal deformation fringe patterns produced by the two earthquakes. We conducted a nonlinear geophysical inversion to estimate the geometric parameters of the earthquakes with the InSAR and GPS measurements. The best-fitting model shows that a thrust faulting on a reverse fault and left-lateral strike-slip faulting on a nearly vertical fault with the centroid depths of 9.3±0.6 and 8.4±0.7 km, respectively, are most likely responsible for the earthquake doublet. The eastern Denali fault (EDF) and Duke River fault are major active faults in the region and the earthquake doublet could be due to reactivation of the part of the two faults system

Rapid Damage Mapping for the 2015 M_w 7.8 Gorkha Earthquake Using Synthetic Aperture Radar Data from COSMO–SkyMed and ALOS-2 Satellites

The 25 April 2015 M_w 7.8 Gorkha earthquake caused more than 8000 fatalities and widespread building damage in central Nepal. The Italian Space Agency’s COSMO–SkyMed Synthetic Aperture Radar (SAR) satellite acquired data over Kathmandu area four days after the earthquake and the Japan Aerospace Exploration Agency’s Advanced Land Observing Satellite-2 SAR satellite for larger area nine days after the mainshock. We used these radar observations and rapidly produced damage proxy maps (DPMs) derived from temporal changes in Interferometric SAR coherence. Our DPMs were qualitatively validated through comparison with independent damage analyses by the National Geospatial-Intelligence Agency and the United Nations Institute for Training and Research’s United Nations Operational Satellite Applications Programme, and based on our own visual inspection of DigitalGlobe’s WorldView optical pre- versus postevent imagery. Our maps were quickly released to responding agencies and the public, and used for damage assessment, determining inspection/imaging priorities, and reconnaissance fieldwork

Early and persistent supershear rupture of the 2018 Mw 7.5 Palu earthquake

The speed at which an earthquake rupture propagates affects its energy balance and ground shaking impact. Dynamic models of supershear earthquakes, which are faster than the speed of shear waves, often start at subshear speed and later run faster than Eshelby’s speed. Here we present robust evidence of an early and persistent supershear rupture at the sub-Eshelby speed of the 2018 magnitude 7.5 Palu, Indonesia, earthquake. Slowness-enhanced back-projection of teleseismic data provides a sharp image of the rupture process, along a path consistent with the surface rupture trace inferred by subpixel correlation of synthetic-aperture radar and satellite optical images. The rupture propagated at a sustained velocity of 4.1 km s^(–1) from its initiation to its end, despite large fault bends. The persistent supershear speed is further validated by seismological evidence of far-field Rayleigh Mach waves. The unusual features of this earthquake probe the connections between the rupture dynamics and fault structure. An early supershear transition could be promoted by fault roughness near the hypocentre. Steady rupture propagation at a speed unexpected in homogeneous media could result from the presence of a low-velocity damaged fault zone

Wpływ opatrunków wytwarzających niewielkie podciśnienie na poprawę gojenia ran u pacjentów z zespołem stopy cukrzycowej stopnia I–II

Cel: Omówienie skuteczności i roli opatrunków podciśnieniowych typu MVD (micropower vacuum dressing) we wspomaganiu gojenia się ran w zespole stopy cukrzycowej stopnia I–II. Materiał i metody: Wybrano 60 pacjentów z rozpoznaniem owrzodzenia stopy cukrzycowej stopnia I–II według klasyfikacji Wagnera i losowo przydzielono do grupy kontrolnej lub grupy eksperymentalnej, po 30 przypadków w każdej grupie. W grupie kontrolnej stosowano konwencjonalne zabiegi i opatrunki nasączone wazeliną, a w grupie eksperymentalnej do standardowego leczenia dołączono opatrunki MVD. Obserwowano efekty leczenia w obu grupach, w tym odsetek wygojeń, procentową redukcję powierzchni owrzodzeń, czas gojenia owrzodzeń, częstość zmiany opatrunków, częstość nawrotów owrzodzeń, zdarzenia niepożądane. Wyniki: Odsetek wygojeń (100%) w grupie eksperymentalnej był wyższy niż w grupie kontrolnej (56,7%); wskaźnik redukcji rany był wyższy niż w grupie kontrolnej (p < 0,05), natomiast czas gojenia, liczba zmian opatrunków i częstość nawrotów w ciągu 1 miesiąca były niższe niż w grupie kontrolnej (p < 0,05). Częstość występowania działań niepożądanych w grupie eksperymentalnej (6,7%) była niższa niż w grupie kontrolnej (46,7%) (p < 0,05). Wnioski: Opatrunki podciśnieniowe typu MVD istotnie wpływają na skuteczność leczenia ran w zespole stopy cukrzycowej stopnia I–II i mają niewiele działań niepożądanych. Jest to skuteczna nowa metoda, która może sprzyjać wzrostowi tkanki ziarninowej i naskórka oraz sprzyjać gojeniu się ran

Ionospheric Correction of InSAR Time Series Analysis of C-band Sentinel-1 TOPS Data

The Copernicus Sentinel-1A/B satellites operating at C-band in terrain observation by progressive scans (TOPS) mode bring unprecedented opportunities for measuring large-scale tectonic motions using interferometric synthetic aperture radar (InSAR). Although the ionospheric effects are only about one-sixteenth of those at L-band, the measurement accuracy might still be degraded by long-wavelength signals due to the ionosphere. We implement the range split-spectrum method for correcting ionospheric effects in InSAR with C-band Sentinel-1 TOPS data. We perform InSAR time series analysis and evaluate these ionospheric effects using data acquired on both ascending (dusk-side of the Sentinel-1 dawn-dusk orbit) and descending (dawn-side) tracks over representative midlatitude and low-latitude (geomagnetic latitude) areas. We find that the ionospheric effects are very strong for data acquired at low latitudes on ascending tracks. For other cases, ionospheric effects are not strong or even negligible. The application of the range split-spectrum method, despite some implementation challenges, largely removes ionospheric effects, and thus improves the InSAR time series analysis results