New LIDAR （Light Detection and Ranging） and sonar imagery have revealed remarkable geomorphic details never seen before and not visible by any other means. Numerous faults and other geologic structures are plainly v...New LIDAR （Light Detection and Ranging） and sonar imagery have revealed remarkable geomorphic details never seen before and not visible by any other means. Numerous faults and other geologic structures are plainly visible on LIDAR and sonar images. Many previously unknown faults criss-cross the islands and large fault scarps are visible on sonar imagery along the margins of the larger islands. Sonar images of sea floor morphology show many submerged faults as long linear scarps with relief up to 300m （1,000 fl）, some of which visibly truncate geologic structures. The San Juan Lopez fault, the largest fault in the islands, extends for at least 65 km （40 mi） from Stuart Island to Rosario strait with a scarp up to 330m （1,000 it） high. Since 1975, the basic structural framework of the San Juan Islands has been considered to consist of five stacked thrust faults, the Rosario, Orcas, Haro, Lopez, and Buck Bay faults, constituting the San Juan Thrust （Nappe） System that has shuffled together far distant terranes. However, the new LIDAR and sonar imagery shows that most of the mapped extent of these postulated faults are actually segments of high angle, dipslip faults and are not thrust faults at all. Thus, the San Juan Thrust （Nappe） System does not exist. The age of these faults is not accurately known and more than one period of high angle faulting may have occurred. Faults shown on L1DAR images of the surface of the islands appear as visible gashes, etched out by erosion of fault zones with few fault scarps. However, the sea floor faults have bold relief and high scarps. A late Pleistocene moraine lies undisturbed across the San Juan Lopez fault.展开更多
Wave steepness is an important characteristic of a high sea state, and is widely applied on wave propagations at ports, ships, offshore platforms, and CO2 circulation in the ocean. Obtaining wave steepness is a diffic...Wave steepness is an important characteristic of a high sea state, and is widely applied on wave propagations at ports, ships, offshore platforms, and CO2 circulation in the ocean. Obtaining wave steepness is a difficult task that depends heavily on theoretical research on wavelength distribution and direct observations. Development of remote-sensing techniques provides new opportunities to study wave steepness. At present, two formulas are proposed to estimate wave steepness from QuikSCAT and ERS-1/2 scatterometer data. We found that wave steepness retrieving is not affected by radar band, and polarization method, and that relationship of wave steepness with radar backscattering cross section is similar to that with wind. Therefore, we adopted and modified a genetic algorithm for relating wave steepness with radar backscattering cross section. Results show that the root-mean-square error of the wave steepness retrieved is 0.005 in two cases from ERS-1/2 scatterometer data and from QuikSCAT scatterometer data.展开更多
文摘New LIDAR （Light Detection and Ranging） and sonar imagery have revealed remarkable geomorphic details never seen before and not visible by any other means. Numerous faults and other geologic structures are plainly visible on LIDAR and sonar images. Many previously unknown faults criss-cross the islands and large fault scarps are visible on sonar imagery along the margins of the larger islands. Sonar images of sea floor morphology show many submerged faults as long linear scarps with relief up to 300m （1,000 fl）, some of which visibly truncate geologic structures. The San Juan Lopez fault, the largest fault in the islands, extends for at least 65 km （40 mi） from Stuart Island to Rosario strait with a scarp up to 330m （1,000 it） high. Since 1975, the basic structural framework of the San Juan Islands has been considered to consist of five stacked thrust faults, the Rosario, Orcas, Haro, Lopez, and Buck Bay faults, constituting the San Juan Thrust （Nappe） System that has shuffled together far distant terranes. However, the new LIDAR and sonar imagery shows that most of the mapped extent of these postulated faults are actually segments of high angle, dipslip faults and are not thrust faults at all. Thus, the San Juan Thrust （Nappe） System does not exist. The age of these faults is not accurately known and more than one period of high angle faulting may have occurred. Faults shown on L1DAR images of the surface of the islands appear as visible gashes, etched out by erosion of fault zones with few fault scarps. However, the sea floor faults have bold relief and high scarps. A late Pleistocene moraine lies undisturbed across the San Juan Lopez fault.
基金Supported by the National High Technology Research and Development Program of China(863Program)(No.2008AA09Z102)Data were provided by the European Space Agency
文摘Wave steepness is an important characteristic of a high sea state, and is widely applied on wave propagations at ports, ships, offshore platforms, and CO2 circulation in the ocean. Obtaining wave steepness is a difficult task that depends heavily on theoretical research on wavelength distribution and direct observations. Development of remote-sensing techniques provides new opportunities to study wave steepness. At present, two formulas are proposed to estimate wave steepness from QuikSCAT and ERS-1/2 scatterometer data. We found that wave steepness retrieving is not affected by radar band, and polarization method, and that relationship of wave steepness with radar backscattering cross section is similar to that with wind. Therefore, we adopted and modified a genetic algorithm for relating wave steepness with radar backscattering cross section. Results show that the root-mean-square error of the wave steepness retrieved is 0.005 in two cases from ERS-1/2 scatterometer data and from QuikSCAT scatterometer data.
