Azimuth ambiguities （ghost targets） discrimination is of great interest with the development of a synthet- ic aperture radar （SAR）. And the azimuth ambiguities are often mistaken as actual targets and cause false ...Azimuth ambiguities （ghost targets） discrimination is of great interest with the development of a synthet- ic aperture radar （SAR）. And the azimuth ambiguities are often mistaken as actual targets and cause false alarms. For actual targets, HV channel signals acquired by a fully polarimetric SAR are approximately equal to a VH channel in magnitude and phase, i.e., the reciprocity theorem applies, but shifted in phase about ±π for the first-order azimuth ambiguities. Exploiting this physical behavior, the real part of the product of the two cross-polarized channels, i.e. （SHVSVH）, hereafter called A12r, is employed as a new parameter for a target detection at sea. Compared with other parameters, the contrast of A12r image between a target and the surrounding sea surface will be obviously increased when A12r image is processed by mean filtering algo- rithm. Here, in order to detect target with constant false-alarm rates （CFARs）, an analytical expression for the probability density function （pdf） ofA12r is derived based on the complexWishart-distribution. Because a value of A12r is greater/less than 0 for real target/its azimuth ambiguities, the first-order azimuth ambiguities can be completely removed by this A12r-based CFAR technology. Experiments accomplished over C-band RADARSAT-2 fully polarimetric imageries confirm the validity.展开更多
In this paper, we made a systematic study on more than 40 years of observational data of ten temporary fault-crossing measurement sites in the capital circle region of China. We calculated horizontal and vertical comp...In this paper, we made a systematic study on more than 40 years of observational data of ten temporary fault-crossing measurement sites in the capital circle region of China. We calculated horizontal and vertical components of fault slip, and horizontal extension or compression components. Considering the tectonic characteristics of the capital circle region and regional seismicity, we analyzed the present fault activity of the capital circle region and the relationship with earthquakes. The results show the complexity of fault activity in the region： the level of activity of all faults is low, most faults are left-lateral strike-slip faults; there is less vertical activity than horizontal activity and crustal movement is controlled by horizontal movement; fault activity and earthquake activity have a certain relationship, regional fault activity increases before an earthquake, and fault activity has certain abnormal features before strong earthquakes.展开更多
基金The National Natural Science Foundation of China under contract Nos 41376179 and 41106153
文摘Azimuth ambiguities （ghost targets） discrimination is of great interest with the development of a synthet- ic aperture radar （SAR）. And the azimuth ambiguities are often mistaken as actual targets and cause false alarms. For actual targets, HV channel signals acquired by a fully polarimetric SAR are approximately equal to a VH channel in magnitude and phase, i.e., the reciprocity theorem applies, but shifted in phase about ±π for the first-order azimuth ambiguities. Exploiting this physical behavior, the real part of the product of the two cross-polarized channels, i.e. （SHVSVH）, hereafter called A12r, is employed as a new parameter for a target detection at sea. Compared with other parameters, the contrast of A12r image between a target and the surrounding sea surface will be obviously increased when A12r image is processed by mean filtering algo- rithm. Here, in order to detect target with constant false-alarm rates （CFARs）, an analytical expression for the probability density function （pdf） ofA12r is derived based on the complexWishart-distribution. Because a value of A12r is greater/less than 0 for real target/its azimuth ambiguities, the first-order azimuth ambiguities can be completely removed by this A12r-based CFAR technology. Experiments accomplished over C-band RADARSAT-2 fully polarimetric imageries confirm the validity.
基金sponsored by the Special Foundation of China Earthquake Administration(HBA2)Beijing Nature and Science Foundation(8022009)+1 种基金Spark Program of Earthquake Sciences(XH12001)Youth Seismic Condition Tracking Subject from China Earthquake Administration(2012020201)
文摘In this paper, we made a systematic study on more than 40 years of observational data of ten temporary fault-crossing measurement sites in the capital circle region of China. We calculated horizontal and vertical components of fault slip, and horizontal extension or compression components. Considering the tectonic characteristics of the capital circle region and regional seismicity, we analyzed the present fault activity of the capital circle region and the relationship with earthquakes. The results show the complexity of fault activity in the region： the level of activity of all faults is low, most faults are left-lateral strike-slip faults; there is less vertical activity than horizontal activity and crustal movement is controlled by horizontal movement; fault activity and earthquake activity have a certain relationship, regional fault activity increases before an earthquake, and fault activity has certain abnormal features before strong earthquakes.
