On August 8, 2017, the Jiuzhaigou Mw 6.5 earthquake occurred in Sichuan province, southwestern China, along the eastern margin of the Tibetan Plateau. The epicenter is surrounded by the Minjiang, Huya, and Tazang Faults. As the seismic activity and tectonics are very complicated, there is controversy regarding the accurate location of the epicenter and the seismic fault of the Jiuzhaigou earthquake. To investigate these aspects, first, the coseismic defor‑ mation field was derived from Global Positioning System (GPS) and Interferometric Synthetic Aperture Radar (InSAR) measurements. Second, the fault geometry, coseismic slip model, and Coulomb stress changes around the seismic region were calculated using a homogeneous elastic half‑space model. The coseismic deformation field derived from InSAR measurements shows that this event was mainly dominated by a left‑lateral strike‑slip fault. The maximal and minimal displacements were approximately 0.15 m and − 0.21 m, respectively, along line‑of‑sight observation. The whole deformation field follows a northwest‑trending direction and is mainly concentrated west of the fault. The coseismic slip is 28 km along the strike and 18 km along the dip. It is dominated by a left‑lateral strike‑slip fault. The average and maximal fault slip is 0.18 and 0.85 m, respectively. The rupture did not fully reach the ground surface. The focal mechanism derived from GPS and InSAR data is consistent with the kinematics and geometry of the Huya Fault. Therefore, we conclude that the northern section or the Shuzheng segment of the Huya Fault is the seismo‑ genic fault. The maximal fault slip is located at 33.25°N and 103.82°E at a depth of ~ 11 km, and the release moment is approximately 6.635 × 10 18 Nm, corresponding to a magnitude of Mw 6.49, which is consistent with results reported
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We successfully monitored the ground deformation of an eruption center during the 2015 phreatic eruption of Hakone volcano, Japan, using ground-based interferometric synthetic aperture radar (GB-InSAR). GB-InSAR has been developed and applied over the past two decades and enables the frequent (< 10 min) aerial monitoring of surfi- cial deformation of structures and slopes. We installed a GB-InSAR 4 days before the eruption of Hakone volcano on June 29, 2015, and monitored the ground deformation of an area where uplift was detected by a satellite InSAR. The ground deformation observed by the GB-InSAR began suddenly on the morning of June 29 almost coincident with the intrusion of hydrothermal fluid that was inferred by other geophysical observations. The hydrothermal crack is considered to have caused the eruption, which was known by an ash fall 5 h later. The GB-InSAR results indicated a significant uplifted area which is approximately 100 m in diameter, and new craters and fumaroles were created by the eruption in and around the area. The displacement reached up to a total of 45 mm until the evening of June 29 and continued at least until the morning of July 1. During our observation, the displacement rate decreased twice, and the timing of each decrease seemed to correspond to the formation of new conduits as implied from geophysi- cal observations.
Abstract. Differential interferometric synthetic aperture radar (DInSAR) is an essential tool for detecting ice-sheet motion near Antarctica’s oceanic margin. These space-borne measurements have been used extensively in the past to map the location and retreat of ice-shelf grounding lines as an in- dicator for the onset of marine ice-sheet instability and to calculate the mass balance of ice sheets and individual catch- ments. The main difficulty in interpreting DInSAR is that im- ages originate from a combination of several SAR images and do not indicate instantaneous ice deflection at the times of satellite data acquisitions. Here, we combine the sub- centimetre accuracy and spatial benefits of DInSAR with the temporal benefits of tide models to infer the spatio-temporal dynamics of ice–ocean interaction during the times of satel- lite overpasses. We demonstrate the potential of this syn- ergy with TerraSAR-X data from the almost-stagnant south- ern McMurdo Ice Shelf (SMIS). We then validate our algo- rithm with GPS data from the fast-flowing Darwin Glacier, draining the Antarctic Plateau through the Transantarctic Mountains into the Ross Sea. We are able to reconstruct DInSAR-derived vertical displacements to 7 mm mean ab- solute residual error and generally improve traditional tide- model output by up to 39 % from 10.8 to 6.7 cm RMSE against GPS data from areas where ice is in local hydro- static equilibrium with the ocean and by up to 74 % from 21.4 to 5.6 cm RMSE against GPS data in feature-rich coastal areas where tide models have not been applicable before. Numerical modelling then reveals Young’s modulus of E = 1.0 ± 0.56 GPa and an ice viscosity of ν = 10 ± 3.65 TPa s when finite-element simulations of tidal flexure are matched to 16 d of tiltmeter data, supporting the hypothesis that strain- dependent anisotropy may significantly decrease effective
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This paper is aimed at exploring a new procedure to provide an alternative solution to the one introduced in  to estimate a reliable atmospheric phase screen (APS) and to discriminate from the global InSAR observed phase, the component given by the topographic height, the phase contribution generated by the atmosphere and the component recorded by the Earth subsidence. The last task is a severe problem since the atmo- sphere is a medium that greatly disturbs the interferometric phase and this occurs in an uncontrollable manner . This separation problem is solved by processing a long temporal series of interferometric SAR observations and the solution is given for highly coherent radar targets. The resulting procedure is based on inverting statistical models where it is necessary to deal with the correlation between the unwrapped phase residuals and the water vapor content of the atmosphere. Note that the latter is often the most important cause of artifacts in SAR interferograms - - . The authors of  demonstrated the feasibility to estimate submeter DEM accuracy and millimetric terrain motion detection once the APS contributions have been estimated and removed. In this context, the present paper proposes a new approach to APS estimation. The technique invokes a direct measurement of the atmospheric phase delay by superimposing a carrier and Doppler frequency variation. The solution is found emulating the atmosphere compensation technique which is largely used by the global positioning system (GPS) where two frequencies are used in order to estimate and compensate the positioning errors due to atmosphere parameters variations - . A sub-chirping and sub-Doppler atmospheric compensation algorithm is derived which allows the successful separation of the height from the Earth movements and the atmosphere parameters from the interferometric phase observed on one InSAR couple. The effectiveness of the new proposed ap- proach is validated using two InSAR couples acquired by the COSMO-SkyMed (CSK) satellite system.
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The application of InSAR encounters problems due to noise appearing in the interferogram phase measurement. There are two types of noises in the interferometric SAR image including the inherent system noise and speckle noise. The speckle noise appearing in interferometric SAR phase images is caused by the coherence interference of waves reflected from many elementary scatters, which degrades the quality of interferogram seriously and makes interferogram reflect the scattering characteristics of the target inaccurately. Therefore, the inhibition of the speckle noise is significant on the SAR imaging process issue. [8, 9] show that the speckle noise reduction processing is necessary for the applications of rapid identification of oil spills and the sea ice segmentation.
The methods to mitigate the atmospheric delay in conventional InSAR data can be classified as 1) integration with dense GPS networks; 2) integration with multi-spectrum water vapor products, for example precipitable water vapor products from Moderate Resolution Imaging Spectroradiometer (MODIS) or Medium Resolution Imaging Spectrometer (MERIS); 3) integration with numerical weather forecast model, e.g. Weather Research and Forecast (WRF) model, and 4) using time-series InSAR techniques, e.g. Small Baseline Subset (SBAS), and Persistent Scatterer (PSInSAR) InSAR (Gong et al., 2011). The GPS method often having difficulties in setting and maintaining GPS sites, while for optical satellite such as MODIS, a full water vapor column is hard to be obtained in most cases due to the persistent block from the clouds (Li et al., 2005). Numerical weather model technique is usually required sufficient available boundary data in order to get accurate and better quality of the forecasts (Gong et al., 2010). Furthermore, this method only aims to reconstruct the atmospheric state at SAR imagery acquisition time but do not solve the decorelation problem in InSAR data.
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Abstract Understanding volcanic unrest is crucial to forecasting eruptions. At active ma ﬁ c calderas unrest culminates in eruption more frequently than at felsic calderas. However, the ma ﬁ c caldera of Alcedo Volcano (Ecuador) has experienced repeated episodes of unrest without erupting, since at least 1992, when geodetic monitoring began. Here we investigate the unrest that occurred between 2007 and 2011 using interferometric synthetic aperture radar (InSAR) data and geodetic modeling. We observe an initial asymmetric uplift of the southern caldera ﬂoor (~30 cm of vertical motion) from 2007 to 2009, followed by subsidence of the uplifted area and contemporary uplift of the northwestern caldera rim between January and June 2010. Finally, from June 2010 through March 2011, caldera uplift resumed. The ﬁ rst uplift episode is best explained by inﬂation of a sill and the activation of an inner ring fault. Successive caldera subsidence and rim uplift are compatible with the withdrawal of magma from the previously in ﬂ ated sill and its northwestern migration. The resumption of uplift is consistent with the repressurization of the sill. This evolution suggests episodic magma emplacement in a shallow reservoir beneath the caldera, with aborted lateral magma migration, probably due to the discontinuous supply from depth. This short ‐ term
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In the last few decades geodetic observations have proliferated with the development of dense permanent Global Navigation Satellite Systems (GNSS) networks such as the GPS Earth Observation NETwork in Japan, the Southern California Integrated GPS Network, the Paciﬁc Northwest Geodetic Array, and the Sumatran GPS Array, and the acquisition of interferometric synthetic aperture radar (InSAR) data from a large variety of satellites. Multiple studies have used the high temporal resolution of continuous GNSS stations to model time-dependent processes including those of slow slip events [e.g., Cervelli et al., 2002; Segall et al., 2006; Schmidt and Gao, 2010; Radiguet et al., 2011; Bartlow et al., 2014; Ozawa et al., 2007; McGuire and Segall, 2003], post seismic slip [e.g., Hsu et al., 2006; Kositsky and Avouac, 2010; Miyazaki et al., 2004; Bedford et al., 2013], and transient deformation [e.g., Mavrommatis et al., 2014]. However, the spatial resolution is dependent on the local GNSS network and thus GNSS station distribution. In contrast, Interferometric Synthetic Aperture Radar (InSAR) has a much ﬁner spatial resolution, on the order of meters, but is limited to longer time scales, with acquisitions every few days at best, and is only sensitive to deformation in the direction of the radar line of sight. Because of complementary advantages, GNSS and InSAR are often used in a joint framework [e.g., Pritchard et al., 2002; Simons et al., 2002; Wright et al., 2004].
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Abstract. We report changes in ice velocity of a 6.5 million km 2 region around South Pole encompassing the Filchner-Ronne and Ross Ice Shelves and a significant portion of the ice streams and glaciers that constitute their catchment areas. Using the first full interferometric synthetic aperture radar (InSAR) coverage of the region completed in 2009 and partial coverage acquired in 1997, we processed the data to assemble a comprehensive map of ice speed changes between those two years. On the Ross Ice Shelf, our results confirm a continued deceleration of Mercer and Whillans Ice Streams with a 12-yr velocity difference of − 50 m yr −1 ( − 16.7 %) and − 100 m yr −1 ( − 25.3 %) at their grounding lines. The deceleration spreads 450 km upstream of the grounding line and more than 500 km onto the shelf, beyond what was previously known. Ross and Filchner Ice Shelves exhibit signs of pre-calving events, representing the largest observed changes, with an increase in speed in excess of +100 m yr −1 in 12 yr. Other changes in the Ross Ice Shelf region are less significant. The observed changes in glacier speed extend on the Ross Ice Shelf along the ice streams’ flow lines. Most tributaries of the Filchner-Ronne Ice Shelf show a modest deceleration or no change between 1997 and 2009. Slessor Glacier shows a small deceleration over a large sector. No change is detected on the Bailey, Rutford, and Institute Ice Streams. On the Filchner Ice Shelf itself, ice decelerated rather uniformly with a 12-yr difference in speed of − 50 m yr −1 , or − 5 % of its ice front speed, which we attribute to a 12 km advance in its ice front position. Our results show that dynamic changes are present in the region. They highlight the need for continued observation of the area with a primary focus on the Siple Coast. The dynamic changes in Central Antarctica between 1997 and 2009 are
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lows the creation of high resolution images by applying a coherent-sum process to measured scattered signals in such a way that the scattered signals are synthetically “back-propagated” to the target surface. In the last few years, synthetic aperture imaging techniques have been adapted to the THz spectral region. However, most of this work is applied at frequencies below 1 THz using microwave-based technologies (e.g. Ref. 16). In contrast, Danylov et al. 17 develop an experimentally-complex THz
The Synthetic Aperture Radar (SAR) is convenient for giving information about earth’s surface by using the respective motion between antenna and its target . In various applications like automatic target detection, surface surveillance, mine detection etc. the SAR images provide very important information. In SAR imagery, one of the main problems is that the image textures are usually contaminated with multiplicative speckle noise which is due to coherent radiation in the process of imaging . The texture present in the images usually contains important information about the scene. The objective of despeckling method is to remove speckle noise and to protect all textural features in the SAR images .
Also, the algorithm is tested on the data of the real experi- ment acquired by IBIS-L GB-SAR system. The site is located at the Kawauchi campus of Tohoku University, Sendai, Japan, as shown in Fig.10. The IBIS-L GB-SAR system used in this study features two horn antennas, one for transmitting and the other for receiving, both with vertical polarization. The system operates in the Ku-band with the center frequency of 17.175 GHz and the bandwidth of 300 MHz. The radar is a stepped-frequency system with variable frequency sampling points that are determined on the basis of the observational range. The entire radar-and-antenna assembly is mounted on a linear rail and it scans about 2 m repeatedly. The 2 m scan spends two minutes and it is repeated every 5 minutes. The system acquires data every 5mm along a 2m scan length at 401 azimuth positions. The rest parameters of the system are summarized in Table I.
significant contributions in this article are: for this suggested GGF-BNLM technique, the nonlinear weight kernel was effectively lowered and the guidance picture was effectively built using maximum probability rule and homogeneity analysis of local areas. Due to its usability in varying weather circumstances, SAR images are commonly used in separate areas. But due to the backscattered radar echoes interference, these are corrupted by multiplicative noise. These findings in the resolution degradation of SAR pictures, making it hard to analyze the SAR image, interpret it and process it. For a SAR picture, despeckling is therefore a main thing.
To avoid confusion however, it must be pointed out that pulse compression technique does not make up to pulse modulation. Instead, it constitutes to frequency modulation, with the name chirp, or linear frequency sweep. Typically there are three basic modulation schemes in radar system, namely pulse, linear FM (LFM) chirp, and phase coded. Frequency modulation is conventionally selected over pulse modulation for its easier signal processing and simpler yet economical hardware implementation. Unlike pulse radar that separates the transmitted and received signals in the time domain, the LFM radar transmits chirp signal at lower power yet processes the received signal in frequency domain, thereby eliminating the need for proper and very precise timing circuitry. Also, LFM radar has no need of a high power source as in pulse radar to generate a short burst of electromagnetic energy. In fact the same average transmitting power can be achieved with lower peakamplitude in typical LFM radars. As a matter of fact, the use of frequency modulation to obtain range information in radar is almost as old as radar itself, dating backto 1924 when Appleton and Barnett used this technique for ionospheric sounding .
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For working on diversity conditions, we compare millimeter wave radar with optical technologies. Despite that optical imaging techniques have better resolutions due to its high center frequency, radar imaging has numerous advantages over traditional optical imaging techniques like Camera and Lidar. It is underlined in  that radar has superior working capacity in any weather condition, including rain, snow and fog. The complex roadway environment for automobile requires uninterrupted remote sensors performing consistantly at inclement weather. The millimeter wave radar is capable of acquiring and tracking all obstacles in its field of view (FOV) under all weather conditions . MMWCSAR is an innovative imaging device capable of working on diversity conditions compared to traditional optical sensors.
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In this paper, a summary of the methods and classification algorithms of synthetic aperture radar images calssification and advantages and disadvantages were discussed. In the unsupervised method Fuzzy C-means algorithm was used to develop two new algorithms, in the first of which Cheng Hung achieved NW-FCM new model using weight feature that performs better in detecting a model for images with more than one class, compared to FCM and FWCM. In the second algorithm Hongelei et al. Markov random fields and have achieved enhanced visual quality classification accuracy, compared to FCM algorithm. Also Anfinsen et al. presented mixed Hotelling-Lawley test statistic as a new test to detect the change in multilook polarimetric radar images and test results showed higher detection rate and lower error rate for this method.
However, such a quasilinear inversion cannot yield full sea state parameters of both windsea (wind waves) and swell, and instead yields the sea state parameters of swell, or more accurately called the parameters of the ocean wave components imaged by spaceborne SAR. Therefore, to overcome such a weakness, various parametric models that directly relate SAR-measured sea surface radar backscatter (radar cross section) to the full sea state parameters of SWH and MWP of both windsea and swell have been proposed 14, 17-18 , which also do not need a priori information and can provide
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The azimuth resolution depends on the distance of the targets from the radar and also on the antenna size; the azimuth resolution deteriorates as the distance is increased or the antenna size is decreased. The antenna size must be very large in order to resolve two targets located at long distance from the radar, for the above example the antenna size must be at least 30 m to distinguish between targets c and d; in some cases the practical implementation of the antenna size is not possible because the required antenna size to obtain an acceptable azimuth resolution must be several hundred of meters or even several kilometers.
T h e im age quality requirem ents specified for ERS-1 require th a t the D oppler frequency be know n to w ithin 50 Hz; this is n o t a tta in a b le using only a ttitu d e d a ta . It can be achieved using D oppler tracking, b u t only a fter the P R F am biguity has been resolved. Any error in th e b eam -centre D oppler frequency introduces an error in th e assum ed sla n t range and th u s into th e range walk correction th a t will be applied during processing. T his results in a significant range displacem ent a t th e two ex trem a of th e synthetic a p e rtu re for a given p o in t ta rg e t. R ange reg istratio n of these ex trem a yields a sufficiently accurate estim ate of th e D oppler frequency to resolve th e P R F am biguity. T his m eth o d requires th e presence of recognizable features w ithin th e im age, and hence is only feasible over land. Over ocean and bland landscapes, th e am biguity can n o t be resolved in this way. However, since th e D oppler frequency of a ta rg e t varies m onotonically over th e synthetic a p e rtu re , only one absolute e stim a te is required for th e elim ination of th e error. F urtherm ore, in ERS-1, th e accuracy of th e Doppler tracker is 50 Hz and hence it m ay be used to correct th e azim uth po inting to ± 0.12°, a figure which is well w ithin th e required azim uth pointing accuracy of ± 0.18°. Hence, it is possible to to ta lly elim inate this source of error. D oppler blocking effects are also said to be negligible [R oth, personal com m unication]. For ERS-1 th e im ages will be processed to have zero D oppler. Hence, th e D oppler equations and derivatives given in Section 3.4 can be greatly simplified;
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For the physical layer of WiMAX, the maximum bandwidth of both OFDM PHY and OFDMA PHY is 28MHz. However, it is much more cost-e ﬀ ective for WiMAX SAR to use the unlicensed frequency bands. For unlicensed bands, OFDM PHY uses 256 subcarriers and OFDMA PHY uses 2048 subcarriers. These parameters are defined in the WirelessHUMAN, whose physical layer is similar to its licensed correspondence. Since the bandwidth in unlicensed band can only be 10MHz or 20MHz, the maximum viable bandwidth B = 20MHz. This bandwidth can support the theoretical range resolution to be 7.5m by the equation in Table 2.2, while the length of an airplane or a vessel is generally over 30m. These targets therefore can be resolved by using WiMAX signal. As mentioned before, WiMAX transmits data or signaling in the basic unit of a frame, which is divided into DL and UL subframes for the TDD mode. As shown in Figure 2.14, a DL subframe is composed of many symbols. Certainly, it increases the throughput and e ﬃ ciency to transmit symbols continuously. However, it could cause di ﬃ culty in the receiver of a monostatic radar, which will be discussed in Section 3.2. Thus, we first only reserve one symbol while nullify other symbols in a DL subframe.
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