Multi-track InSAR data have been widely applied to decompose 2D (East-West and Up-Down) co-seismic deformation in order to intuitively interpret the co-seismic deformation. Most of the previous efforts well studied the decomposition of single earthquake deformation using a pair of ascending and descending InSAR data. However, the deformation decomposition of multiple earthquake events in a short time period is rarely discussed and hard to implement. That's because it's hard to make sure that deformation related to each earthquake can be imaged by a pair of ascending and descending track. In this paper, a Pseudo-Small BASeline (SBAS) method is developed to decompose 2D deformation of each earthquake in a sequence event. The rationale behind is that several interferograms with different imaging geometries contain co-seismic deformation related to single or multiple earthquakes, and it provides us the opportunity to separate the 2D deformation of a single or multiple events by fusing the short temporal baseline interferograms from multi-track and multi-temporal SAR observations. The proposed method has two parts. The first part is to correct phase unwrapping errors using a compressed sensing method based on redundant SBAS interferograms. In the second part, we incorporate strain model and the conception of SBAS technique into 2D deformation decomposition. We used our proposed Pseudo-SBAS method and four tracks Sentinel-1 data to study the deformation decomposition of an earthquake sequence hit the Central Greece in March 2021. The comprehensive comparisons on synthetic and real Sentinel-1 data confirm the validity of the proposed method. The experimental results also indicate that a triggering mechanism of cascading rupture process can explain the occurrence of these three sequent earthquakes, and the decomposed post-seismic deformation of the first earthquake in EW direction move towards the opposite direction to the co-seismic deformation.
This study developed an experimental system based on Joule heat of sliding-pressure additive manufacturing (SP-JHAM), and Joule heat was used for the first time to accomplish high-quality single-layer printing. The roller wire substrate is short-circuited, and Joule heat is generated to melt the wire when the current passes through. Through the self-lapping experimental platform, single-factor experiments were designed to study the effects of power supply current, electrode pressure, contact length on the surface morphology and cross-section geometric characteristics of the single-pass printing layer. Through the Taguchi method, the effect of various factors was analyzed, the optimal process parameters were obtained, and the quality was detected. The results show that with the current increase, the aspect ratio and dilution rate of a printing layer increase within a given range of process parameters. In addition, with the increase in pressure and contact length, the aspect ratio and dilution ratio decrease. Pressure has the greatest effect on the aspect ratio and dilution ratio, followed by current and contact length. When a current of 260 A, a pressure of 0.60 N and a contact length of 1.3 mm are applied, a single track with a good appearance, whose surface roughness Ra is 3.896μm, can be printed. Additionally, the wire and the substrate are completely metallurgically bonded with this condition. There are also no defects such as air holes and cracks. This study verified the feasibility of SP-JHAM as a new additive manufacturing strategy with high quality and low cost, and provided a reference for developing additive manufacturing technology based on Joule heat.
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