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This field report describes two deployments of heterogeneous unmanned marine vehicle teams at the 2011 Great Eastern Japan Earthquake response and recovery by the Center for Robot-Assisted Search and Rescue (USA) in collaboration with the International Rescue System Institute (Japan). Four remotely operated underwater vehicles (ROVs) were fielded in Minamisanriku and Rikuzentakata from April 18 to 24, 2011, for port clearing and victim recovery missions using sonar and video. The ROVs were used for multirobot operations only 46% of the time due to logistics. The teleoperated ROVs functioned as a dependent team 86% of the time to avoid sensor interference or collisions. The deployment successfully reopened the Minamisanriku New Port area and searched areas prohibited to divers in Rikuzentakata. The IRS-CRASAR team planned to return from October 18 to 28, 2011, with an unmanned aerial vehicle (UAV), an autonomous underwater vehicle (AUV), and an ROV to conduct debris mapping for environmental remediation missions. The intent was to investigate an interdependent strategy by which the UAV and AUV would rapidly conduct low-resolution scans identifying areas of interest for further investigation by the ROV. The UAV and AUV could not be used; however, the ROV was able to cover 80,000 m2 in 6 h, finding submerged wreckage and pollutants in areas previously marked clear by divers. The field work (i) showed that the actual and planned multirobot system configurations did not fall neatly into traditional taxonomies, (ii) identified a new measure, namely perceptual confidence, and (iii) posed five open research questions for multirobot systems operating in littoral regions. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Abstract: Since the middle Miocene, the Izu–Bonin arc (IBA) has been colliding from the south with the Honshu arc in central Japan associated with subduction of the Philippine Sea plate (PSP). This process is responsible for forming a complex crustal structure called the Izu Collision Zone (ICZ). To obtain direct evidence of the deep structure dominated by collision and subduction, an intensive seismic experiment using explosive and vibroseis sources was conducted in the eastern part of the ICZ. CMP reflection and refraction/wide-angle reflection data were acquired on a 130-km-long seismic line crossing the Kanto Mountains (KM), the Tonoki–Aikawa Tectonic Line (TATL) and the Tanzawa Mountains (TM) from north to south. The TATL is considered to be a collision boundary separating the Honshu arc (KM) from the IBA (TM). The structural model constructed by refraction tomography and forward ray tracing shows remarkable lateral velocity variation across the TATL and some clear reflectors in the deep crust. A north dipping reflector beneath the KM was interpreted to be the deeper extension of the TATL. From the geometry of reflectors, we interpret the Tanzawa block is delaminated from the subducting slab due to the collision to form a wedge-like body thrusting between the upper and lower crust of Honshu. The TM itself shows a velocity structure almost consistent with the upper part of the crust of the Izu intraoceanic arc, south of our study area. The relocated hypocenter distribution using our velocity model shows high seismic activity concentrated around the collision boundary, which is in a marked contrast of low seismicity within the Tanzawa block. These features of seismicity are strongly dominated by the collision of the IBA with the Honshu arc. [Copyright &y& Elsevier]

Abstract: The southwestern Kuril Arc, which is not affected by a series of accretion and collision processes, is one of the most important experimental sites among the world arc–trench systems for investigating the evolution of arc crust. Published petrological and seismic studies have shown that, in south-central Hokkaido, the upper part of the Kuril Arc crust is thrusting upward toward the west while the lower part is descending downward in the same direction. Among several hypotheses for formation of continental crust, we discuss the role of delamination of the island arc lower crust based on geochemical and seismic velocity structure models. Seismic velocity structure is obtained from an onshore–offshore seismic survey across the southwestern Kuril Arc–Trench system. The structure in the back-arc area shows a thick accretionary complex formed by Paleogene accretion and collision. Based on published seismic results, this accretionary complex is considered to continue on land to the Cretaceous accretionary complex observed in the Hidaka Belt. The structure of the Kuril Arc appears characteristic of upper crustal andesitic rocks (6.0–6.2 km/s) and thick middle to lower crust (6.5–7.3 km/s). Based on published geochemical study, we consider a geochemical model of simple crustal evolution explaining the mechanism of generation of andesitic rocks on the Kuril Arc. Each volume of andesitic, basaltic, and mafic layers estimated from the geochemical model is consistent with those obtained from the seismic velocity model. Crustal composition estimated from the geochemical model and major-element chemistry of the volcanic rocks in the Kuril Arc indicate that mechanical delamination is insufficient to cause the oceanic island arc crust to evolve into continental crust. [Copyright &y& Elsevier]

Abstract: This paper aims to assess quantitatively the actual visual environment of uncontrolled urban downtown intersections in Japan in relation to frequently occurring crossing collisions and to discuss the safety countermeasures for them. In Field Study 1 dealing with direct visibility, our ultra-wide-angle photograph analysis revealed that most of the right/left-ward visible range at 11 intersections were insufficient to check safety, and the quality of direct visibility was closely associated with causing crossing collisions. The countermeasures to reduce a blind area were determined to be a top priority. In Field Study 2 dealing with indirect visibility, more than half of the 25 traffic convex mirrors had marked shortcomings for preventive safety, and ergonomics guidelines ensuring indirect visibility were proposed for installing traffic convex mirrors. Low-cost/low-technology-oriented countermeasures are highly recommended to obtain clear/sufficient images of crucial information satisfying drivers’ requirements on traffic convex mirrors in accordance with those ergonomics guidelines was highly recommended. Crossing collisions could be prevented by improvement of poor direct and indirect visibility. [Copyright &y& Elsevier]

A transition and subduction zone adjacent to the Ryukyu Arc, Ryukyu Trench, and Okinawa Trough, extends between southern Japan and northeastern Taiwan. It is generated during the northwestward subduction of the Philippine Sea Plate, which lies the Eurasian Plate along the Ryukyu Trench. The movement of the Philippine Sea Plate is hindered at the northeastern corner of Taiwan, which causes complicated structure of the Philippine Sea Plate at the western end of the Ryukyu subduction zone. Development of the active subduction and transition boundary near the western Ryukyu Arc is evaluated statistically by using displacements derived from GPS site data. The statistical model shows that the absolute displacement derived from GPS measurements of nearly 8 years indicates a maximum spatial variation of 0.625 m. Three trends are observed for such long-term progress, and use of linear regression also reveals quite good consistency between the data and statistic models. Such rate is also elevated following the trend development. Southeastern and nearly horizontal movement is suggested to the main development of for the site movements, it is likely related to the tensional activity adjacent to this boundary. [ABSTRACT FROM AUTHOR]

Highlights the XXI International Conference on the Physics of Electronic and Atomic Collisions held at Sendai, Japan on July 22 to 27, 1999. Organizers of the conference; Issues discussed at the conference; Studies presented at the conference.

Focuses on the shallow deformation in the Cape Erimo Area in central Hokkaido and discusses the process of collision at the arc-arc junction. Tectonic framework of arc-arc junction; Geologic outline of the Cape Erimo area; Deformation phase and mode of the Erimo formation.