Approach for the Realisation of Sea Bottom Crustal Deformation Observations Targets and Tactics in Waters around Japan

The Japan Hydrographic Department (JHD), has been pursuing two approaches using acoustic geodetic techniques to observe the crustal deformations on the deep sea floor to understand the mechanisms of major interplate earthquakes at subduction plate boundaries. One is the repeated acoustic ranging between two stations on the sea floor. The other is the linkage of GPS precise positioning of a sea surface platform and acoustic ranging between the sea surface and sea bottom transducers. The applicability of both methods to detect the plate motions of oceanic crust has already been demonstrated, through sea trials . In the JHD, there is a plan to realise operational surveys for the detect ion of sea bottom crustal deform ations

Basic properies of beam flatness analyzer (THEBES 7000)

癌の有力な治療法の1つである放射線治療はシステム全体の許容誤差が±5％と、正確な治療が要求されている。正確な線量を正確な場所に照射されなければならない。そのためには日頃から照射装置のQuality Control が重要である。Beam平坦度の測定はその中でも、重要な項目で1／6月の測定頻度が勧告されている。今回、市販のBeam Flatness Analyzer (7000型 THEBES) を使用する機会を得たので、その基礎的性能であるChamber 相互の感度のちがい、測定値の再現性、識別可能な最小線量について実験を行った。各項目とも誤差が非常に少なく、日常の使用に際してそのデータは十分信頼できるものであることがわかった。Lrradiation, which is one of the effective therapies to Cancer, is required to be accurate within ±5% of the tolerable error of the total system. An accurate dose has to be irradiated accurately at a target volume. For that Quality Control of the irradiation equipment is cotinually important. As the measurement of Beam Flatness is an important item, it is obligated to be measured once a week. In this paper as we have an opportunity to use a Beam Flatness Analyzer sold on a corporation of medical instrument, we experiment about the difference of sensitivity of mutual Chamber which is its basic property, the reproducibility of the measured score, and the minimum value of measuralbe dose. We find that the difference in every item is so small that its data is very reliable in a daily use

An Experimental Multi-disciplinary observatory (VENUS) at the Ryukyu Trench using the Guam-Okinawa Geophysical Submarine Cable

A multidisciplinary Ocean Bottom Observatory (MDOBO) was installed on VENUS (Versatile Eco-monitoring Network by Undersea-cable System) a depth of 2,170 meters on the slope of the Ryukyu Trench. In this context, Eco- refers to both economic (e.g., earthquake hazard mitigation) and ecological motivation. The first step in this instillation was to insert a telemetry/power system into the submarine coaxial cable; this system could then service the MODOBO, which consist of seven major bottom sensor packages. During August-September 1999, using a deep-towed unit and both manned and unmanned submersibles coupled with precise ship navigation, the MDOBO system and its attendant cables were deployed over a range of distances from 80 m to 1 km from the telemetry system, with several meter allowance for navigational uncertainty in positioning. The unmanned submersible then extended the multi-conductor extension cables from the instrument units toward the telemetry system and connected them to undersea mateable connectors on a junction box installed on the submarine cable. The MDOBO collected one and half months of continuous records. Several kinds of useful data were collected after installation, including an aftershock (Ms=6.1) of the 1999 Chi-Chi earthquake (Ms=7.7) in Taiwan