The Doppler weather radar on board the research vessel Mirai, which was installed in 1998, was replaced by a dual-polarization Doppler weather radar in 2014. This study explores the beam blockage for both radars on board the Mirai. Reflectivity data from long-term observations were used to calculate the probability of detection (POD) at a given range, azimuth, and elevation relative to the Mirai. Azimuthal sectors suffering from beam blockage caused by the infrastructure of the Mirai were characterized by pronounced minima of the POD in their centers and significant discontinuities of the POD on their edges. An objective method was developed to ascertain the boundaries of the blocked sectors based on the rate of change of the POD gradient along the azimuthal direction. According to the distinct signatures of the POD, detailed beam blockage information for both radars was identified in different ship-relative elevations. Although beam blockage for both radars occurred from low to high elevations, the total azimuths of the low-level blocked sectors for the dual-polarization Doppler radar decreased by more than half. This improvement was attributed to the higher location of the antenna for the dual-polarization Doppler radar. This accurate beam blockage information will facilitate the quality control of the Mirai radar data.
In recent years, we conducted marine seismic surveys in the Japan Sea with the research vessels of the Japan Agency for Marine-Earth Science and Technology (JAMSTEC). In these surveys, high quality bathymetric data by the multi-narrow beam echo sounder have been obtained simultaneously with navigation of vessels. Bathymetric data are one of the important key to understand tectonic history and earthquake source fault model in the Japan Sea. Therefore, the effective use of high quality bathymetric data makes progress in the integrated study of the relationship between active structure, seismicity, and crustal structure in the Japan Sea. In this report, we describe about red relief image map and DEM (Digital Elevation Model) data which are created by the integration of topographic data in and around the Japan Sea.
Seismic tomograms are the images of Earth's internal characteristics that help us understand geophysical phenomena. As a website at http://csmap.jamstec.go.jp, CSMAP provides an easy way to select and view Earth's seismic tomograms through a working web browser, acting as a graphical user interface to the underlying tomogram engine. The tomogram engine computes Earth's cross section tomograms with a depth range from Earth's surface to Core-Mantle Boundary (CMB) based on the seismic velocity perturbation model selected by the user from the three predefined models available in the website. Given a tomographic model and a cross section profile specified by two geocoordinates, CSMAP tells the engine to generate a tomogram. It sends the result back to the user in an HTML page, or as a PDF or Postscript file when the engine finishes computation.Written mostly in Java, CSMAP is run by Apache Tomcat on a Linux server. It works with all major web browsers including Google Chrome, Firefox, and Microsoft Internet Explorer. The user interface was designed to be simple and intuitive, yet it provides necessary help texts in tooltips and introduction pages in more details. With its small footprint on the server, CSMAP is easy to install and maintain. Since its launch on a JAMSTEC's public server in June 2015, the site has been running constantly and reliably without any major problems.In this report, we introduce CSMAP by presenting its background, system structure, and webpage layouts and usage. The usage statistics of the site for the initial 3 months are also presented.
Effects of soaking, stirring, and milling were investigated to standardize the washing method used for drill cutting samples. Drill cuttings are fragments of solid material ground by a drill bit at the bottom of a hole. They are recovered on the ship in riser drilling as a component of the circulating drilling mud. Removal of drilling mud from the surface of cutting samples must be done before cutting samples are analyzed. Cutting samples from IODP Expedition 337 were used in test experiments. The samples were analyzed before and after soaking, stirring, and milling with XRD, XRF, an elemental analyzer and a carbonate analyzer. Results show that Na and K contents are reduced by the removal of drilling mud. However, changes that occur after 6 h of soaking are rather minor. These results suggest that stirring of cuttings in heated seawater at 40℃ for 6 h after quick washing is effective for XRF and TOC analyses.