Optically stimulated luminescence (OSL) dating provides an absolute age control for marine deep-sea sediment. Optical history of target minerals such as quartz and feldspar in the sediment is critical for the OSL dating that includes not only natural processes but also artificial exposure process to the daylight during sediment coring and sampling. An onboard complete optical covered procedure for marine sediment coring from deep-sea bottom for the OSL sample was developed in order to avoid any optical exposure during the sediment sampling. The methods includes: (1) a black-colored inner tube is set up in the outer core barrel of sediment corer before sediment coring, (2) the black inner corer is carefully drawing out from outer core barrel after returning of the corer on deck, (3) both ends of section (top and bottom parts of the section) are covered by opaque caps just after sectioning of the core, (4) splitting of the whole-rounded core is carried out during the night on deck. The section is moved in the dark room and split into half-semicircle pillar-shaped core by using wire in the room, (5) split sections are pack into large opaque plastic bag and store in refrigerator (3 degree Celsius) before sampling, (6) aliquot sample for the OSL is taken from each section in the dark room and stored in small opaque plastic bag before analysis, (7) any sample preparation for the OSL is performed in the dark laboratory. By following the methods, only top and bottom parts of the section and outer rim of the sediment core may be affected by light exposure during the core processing, but the central part of the aliquot slice of the section is completely safe by exposure to daylight and available for the OSL measurement. The sediment coring in the complete dark side following the method results in fine OSL dating. The proposed procedure of this study will be a methodological standardization of optical covered sediment coring of deep-sea sediment.

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This paper proposes a new method to estimate stress of concrete structures. The calcite twin is intra-crystalline deformation that increases with stress, and calcite-twin piezometer has been applied in pure-calcite rock. However, it has been hardly used for polymineralic rocks due to uncertain of inner stress field of a rock. Discrete Element Method (DEM) can simulate deformation of aggregate, and it reveals that mean stress of particle is proportionate with applied force to an aggregate. Increase of calcite-twin with applied-force within a polymineralic material was confirmed by a rock compression experiment. These suggest that the calcite-twin piezometer is applicable to polymineralic materials, and this technique has potential to contribute to safety assessments of concrete structure (Publication of Unexamined Application 2008-286689).

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The vitrinite reflectance is a geothermometer in diagenetic to low grade metamorphic rocks, and standardized in ISO, JIS and ASTM. However ordinal method can not be applied for small grains less than 75 μm. The criteria based on thermo-plasticity can recognize vitrinite in small particles. A new device with double illuminations of the Keller type for lighting wide area and the Critical type for lighting spot area was developed for spot analysis with wide field observations. This system enables to make thermal mapping along fault zone and estimation of paleo-temperature of fine-grained sediments. A part of this method and apparatus is registered as the patent 2007-132795 in Japan.

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We had developed a new particle trapping system, “TSUBUTRA”, to collect coarse grains (>67 micrometer) with measurement of grain size analyzer. Eventually, maximum 30 series of coarse grain fraction automatically collected with grain size distribution at one sequence. The system is consisted of controller unit, auto sampler unit, and trapping tubes with mesh sheets. An optical sensor generates a start trigger signal from a movement of auto sample changer of the grain size analyzer, and another optical sensor generates a stop trigger signal from the auto sampler unit, to separate individual trapped samples linked to sequential measurements of grain size distribution. Mesh sheet equipped in the auto sampler unit certainly traps >67 micrometer particles from drain of the grain size analyzer subsequently to the measurement. The TSUBUTRA enable us to observe and identify the grain composition with the size distribution.

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Microtome, lathe, and hand-sampling under the microscope have been used for the microsampling methods of the fossils and rock samples. However, these methods were difficult to get samples on micrometer scale precisely. GEOMILL326 provides a computer controlled microsampling technology on 1/1000mm scale. GEOMILL326 is effective for the microsampling along the growth banding such as coral, bivalves, stalactites, and useful for cutting of the metal with a single crystal diamond drill bit. Moreover, an apparatus of collecting powder samples to the container for chemical analyses with high recovery rate was also developed.

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A vacuum sample crushing system equipped with a quadrupole residual gas analyzer was operated out of laboratory and was proved to perform reliable sample analyses of noble gases and coexisting carbon dioxide, water, and nitrogen. Careful sealing at disassembly and assembly maintained the apparatus under ultra high vacuum of 10^-5 Pa that is comparable to the pressure in usual operation. The analyses of a gas rich basaltic glass from East Pacific Rise, 6K834R4, represented minimum detection limit down to 7 × 10^-7 Pa as a partial pressure in the instrument; the value was determined as the difference between an apparent value of change from a base line. The result demonstrates the potential of “on-site” gas analyses on fluids on research vessels or vehicles when the sufficient electric power is supplied and the apparatus is treated carefully at transportation and assembly.

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Frictional melting experiments were performed on fine grain homogeneous gabbroid with high temperatures induced by frictional heating using a high-velocity apparatus. We examined whether rapid fault movement can equilibrate fault rock gas with atmospheric components by measuring volatile gas and noble gas isotopes from a gabbroid sample using a quadrupole mass spectrometer to detect released gas from the simulated fault rock.
The anticipated rapid equilibration of volatiles during the frictional melting of rocks implies that the noble gas and volatile were released and mixed with the atmosphere during this experiment. Gases released from the sample were collected in a small aluminum tube in nitrogen atmosphere before and after the frictional melting experiment. The gas comprised carbon dioxide, water vapor, hydrogen, helium, and other noble gases. The He/Ar ratio and H₂ concentration are higher than the pre-analysis of N₂ atmosphere. This release of volatiles is consistent with the pseudotachylyte-like post experimental texture of specimen. It is also consistent with the co-seismic geochemical anomaly observed along a natural fault system.

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A two-step chemical procedure to separate Sr from whole igneous rock sample has been developed for the analysis of Sr isotopes by thermal ionization mass spectrometry (TIMS). Firstly, a Sr-bearing fraction and a REE fraction are separated from the major elements of a decomposed sample solution using H⁺ form cation-exchange chromatography. Then the Sr fraction is purified in a second column using extraction chromatography and a Sr specific resin. For small amounts of sample (< 0.1 mg) obtained by micro-milling, only the second step of column separation is applied, directly separating the Sr fraction from the decomposed sample solution. The total procedural blank of these chemical separation procedures are very low, comparable to the lowest blank levels ever reported. The purified Sr is loaded on to a single Re-filament with a Ta ionization activator and measured using TIMS in static multi-collection mode. The mean value and reproducibility for standard ⁸⁷Sr/⁸⁶Sr in NIST SRM 987 with Sr loads of 100 ng and 5 ng are 0.710240 ± 0.000012(2σ, n = 12) and 0.710248 ± 0.000022 (2σ, n = 7), respectively. These values agree well with those from previous studies. Additionally, Sr isotope ratios measured in GSJ igneous rock reference materials JB-2, JA-1 and JR-1 are within error of values from previous studies, verifying the versatility of the technique reported in this study.

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We report a procedure that separates Nd from silicate rock samples using cation exchange chromatography allowing ¹⁴³Nd/¹⁴⁴Nd ratio analyses to be performed by thermal ionization mass spectrometry (TIMS). The procedure obtains the Nd fraction using a two-step column separation. First, a rare earth element (REE) fraction is separated via a cation exchange column with HCl as the eluent. Then, Nd is separated from this REE fraction using a second cation exchange column with α-hydroxy isobutric acid (HIBA) as the eluent. The procedural Nd blanks measured for each step are very low and negligible for ¹⁴³Nd/¹⁴⁴Nd ratios in natural rock samples. The Nd yields are high, with more than 90 % of Nd recovered during each step. Repeated analysis of ¹⁴³Nd/¹⁴⁴Nd ratios in the JNdi-1 standard solution gave a mean value of 0.512096 ± 0.000014 (2 SD, n = 144, RSD % = 0.0014), which is in good agreement with those reported in previous studies. The ¹⁴³Nd/¹⁴⁴Nd ratio obtained for the corrected JNdi-1 fractions using the technique in our laboratory was 0.512094 ± 0.000011 (2 SD, n = 4). We also measured ¹⁴³Nd/¹⁴⁴Nd ratios in several geochemical igneous rock reference materials (JB-la, JB-2, JA-1, and JR-1) producing mean values consistent with available data. These results indicate that the technique for Nd isotope analysis employed at our laboratory provides reliable and accurate data for geochemical studies.

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A fully-automated (FA) technique applying ²⁰⁷Pb-²⁰⁴Pb double spike (DS) to thermal ionization mass spectrometry (TIMS) has been developed (FA- DS- TIMS). A long-term baseline is measured prior to the sample measurement runs and is applied to all of the acquired sample data, avoiding sample wasting caused by frequent baseline measurements during sample runs. FA- DS- TIMS offers reliable fully automated sequential analyses of 10 samples in one batch, including 10 natural runs and 10 runs doped with a spike enriched ²⁰⁷Pb and ²⁰⁴Pb. This cuts operating labor costs, although the measurement time is longer than a conventional TIMS or an identical run using multi collector-inductively coupled plasma-mass spectrometry (MC-ICP-MS).
The isotopic ratios of the ²⁰⁷Pb-²⁰⁴Pb double spike used in this study are ²⁰⁶Pb/²⁰⁴Pb = 0.10203, ²⁰⁷Pb/²⁰⁴Pb = 3.8717 and ²⁰⁸Pb/²⁰⁴Pb = 0.18865 when normalized to NIST SRM 982 ²⁰⁸Pb/²⁰⁶Pb = 1.00016. Average values for NIST SRM 981 containing 7.5 and 15 ng Pb are ²⁰⁶Pb/²⁰⁴Pb = 16.9390 ± 0.0017, ²⁰⁷Pb/²⁰⁴Pb = 15.4972 ± 0.0017, ²⁰⁸Pb/²⁰⁴Pb = 36.7213 ± 0.0045 (errors are 2SD, n = 12). These are within error of recently reported values obtained by DS-TIMS and DS-MC-ICP-MS. The reproducibility of ²⁰⁸Pb/²⁰⁴Pb in this study is 0.003% using 15 ng Pb, and 0.009% using 7.5 ng Pb. These are similar to, or better than, those reported by various other methods. The average values for JB-2 containing 20ng Pb are ²⁰⁶Pb/²⁰⁴Pb = 18. 3419 ± 0. 0027, ²⁰⁷Pb/²⁰⁴Pb = 15.5622 ± 0.0026, ²⁰⁸Pb/²⁰⁴Pb = 38.2814 ± 0.0078 (errors are 2SD, n = 5) and are comparable to those reported in recent studies. These results show that the new technique is reliable in terms of both accuracy and precision.

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For understanding mechanisms of large earthquakes and tsunami, JAMSTEC has been conducting active-source seismic surveys using own seismic system since 1995. The seismic system was mounted on the new R/V Kairei in 1997. In 1999, the seismic system was upgraded for larger volume airgun array (total volume of 197 L), which was mounted on both R/Vs Kairei and Kaiyo. Operation of 100 OBS was also started in 1999. In 2004, the number of section of the streamer cable on the R/V Kairei and OBS were increased for intensive surveys in the Izu-Bonin-Mariana region. The seismic system has provided several important new findings concerning seismogenesis and arc evolutions. However, further improvement of data quality was required for making integrated study of seismic study and material study, which was necessary for the IODP study. To meet the requirements, the new seismic system with a tuned airgun array and a streamer cable with dense group interval have been fit out to R/V Kairei in 2008, and the required capability have been confirmed by field data. Future improvements would be necessary to achieve future scientific requirements.

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Spatio-temporal distribution of temperature beneath the seafloor provides essential information on the thermal and hydrological structure and dynamics. We developed some long-term temperature monitoring systems for observation at seafloor, in a few-m-deep hole, and in deep boreholes. Measurements in a shallow hole were carried out at a hydrothermal field in the southern Mariana Trough and in the western Sagami Bay, and thermistor array system was tested in two onland boreholes in the northeastern Japan for up to 1.5 years. The thermistor elements coated with ‘Teflon’ was proved to be stable and reliable in a temperature range of 0 to 80 °C for more than one year. Shorter time scale and rather aperiodic variations in temperatures were commonly observed in boreholes. These variations would result from convection or any kind of flow within the hole. Such variation can be as large as any signal from the formation, so more careful assessment is necessary for the deep-borehole observatory that is in development at JAMSTEC.

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During the past five years, the electro magnetic (EM) team of the Japan Agency for Marine Science-Technology (JAMSTEC) has conducted many observations to investigate the crustal and mantle structure in pursuit of various scientific aims in collaboration with other universities and institutes. Around the Nankai subduction zone, we constructed a crustal and regional resistivity model, and detected the low resistivity zone with subduction. Moreover, we developed new geophysical survey tools—the small ocean bottom electro magnetometer (OBEM) and the deep-towed DC resistivity survey system—to investigate the shallow crustal structure. We also conducted an ocean bottom EM array study in the Philippine Sea and other areas to investigate the mantle structure using long-term OBEMs, thereby obtaining high-quality EM data.

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Near-bottom magnetic measurements provide us high-resolution magnetic anomaly. The high-resolution anomaly is valuable for the studies of the detailed magnetization structure of ocean crust and paleointensity recorded on the ocean crust. The measurements using a submersible have advantages to make the magnetometer system simple and to incorporate other observational results obtained by the submersible, such as seafloor pictures and samples that are informative for geology. A submersible usually moves at a height of several meters above seafloor, therefore the magnetic anomaly has a resolution of several meters. Magnetic measurements using the submersible Shinkai 6500 have been conducted several times, and experiences and scientific results have been accumulated. On the other hand, problems regarding the magnetic measurements were brought out. Because the submersible observation usually gives priority to geological observation, the navigation is not suitable for magnetic measurements. The restricted sensor position and the short track length are also disadvantages for the magnetic study. There is room for improvement in the magnetic calibration and operation. For the future, improvement of the measurement method is critically important. The near-bottom magnetic measurements with the submersible expand the range of the submersible study and provide additional information about lithology which may not be visible at the seafloor, and the seafloor age with a high resolution.

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Marine sediments provide valuable information for a continuous geological record. Piston-type corers (conventional piston corer, and Integrated Ocean Drilling Program piston corer such as Advanced Piston Core System) are commonly used to collect sediments from the seafloor. The piston-type corer can recover a relatively longer sequence of sediment than that collected by a gravity-type corer. It owes a negative pressure produced by piston-system which makes sediment entering easier into tubes. However an inappropriate working of piston system will result in disturbing the texture and structure of sediment core. The disturbance possibly makes alternations on basic parameters such as length and physical properties. Although the disturbance is invisible sometimes, it can be detected by magnetic remanent directions and anisotropy of magnetic susceptibility.

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A seismometer installed on the seafloor is affected by water flow, which could cause a noise in seismic records. The noise is significant especially for low frequencies below 0.1 Hz. For seafloor seismic observatories installed by free fall from a ship, it should be important to improve seafloor coupling of seismometer for reducing the low frequency seismic noise. In order to seek for an installation method that gives a better low frequency performance of seismometers, we conducted an installation experiment using two broadband ocean bottom seismometers with different types of anchor. The two seismometers were placed closely, within 150 m to each other: one with a conventional grid type anchor and the other with a wide planar anchor. The wide planar anchor was used to improve the seafloor coupling of seismometer. The experiment was conducted in the Kumano Basin off Kii Peninsula, from late December, 2007 to early February, 2008. For horizontal components, a noise level obtained from the seismometer with the planar anchor was comparable to that from the seismometer with the conventional anchor. For the vertical-component record, however, the seismometer with the planar anchor had the better noise performance than the seismometer with the conventional anchor at frequencies lower than 0.01Hz.

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A deep-sea differential pressure gauge (DPG) is very sensitive pressure sensor suitable for observation for earthquakes and acoustic phenomena in frequencies 10mHz to 1Hz, providing much lower noise floor compared to existing quartz pressure gauge. Frequency response of DPG is affected by temperature and pressure environment where the sensor is installed. Methods to estimate sensitivity and frequency response of DPG were developed, by comparing pressure data with those from quartz pressure gauge of Paroscientific, Inc. Two calibration methods to apply low frequency pressure change were experimented, one in the seafloor, and the other in a laboratory. Using these methods, precise sensitivity and frequency response calibration of DPG can be practiced.

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The existence of fluid in seismogenic zones plays a key role in great earthquakes. Data on electrical conductivity structures obtained by electromagnetic surveys across the great earthquake zones show that the seismically locked zones correspond to low conductive zones. This low conductivity is possibly interpreted as relatively low fluid content in rock or sediment. For more discussion on the role of fluid in earthquake occurrence, we have recently started an electromagnetic and seismological monitoring project using long submarine cables off Toyohashi, in the southwest part of Japan's main island. The cables are located on the Tokai seismogenic zone, where both slow-slipping and locked zones are obvious by GPS observation. We constructed a seafloor observatory at the tip of the western cable, including a seismometer, pressure gauges, a magnetometer, voltmeters, and thermometers. These sensors measure and transfer data on the seafloor environment in real time. The data will be used for passive and active monitoring below the seafloor, including in the Tokai seismogenic zone.

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We have constructed a data base of seismic travel times, which should be used to improve our seismic tomography model. We measured absolute arrival times of several seismic phases such as P, PcP, S etc using hand-picking method and PP-P, S-P differential travel times and relative P travel times between different two stations using cross correlation techniques. We use both of broadband and short period waveform data collected from all over the world including ocean bottom seismometers. At present, we have measured totally about 150,000 of various types of travel times.

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We have developed a new system to visualize observation data obtained in JAMSTEC research vessels. We use Google Earth as a data browser. Google Earth supports an XML-based language, called KML (Keyhole Markup Language), to plot data on Google Earth. We have developed a program, called KML generator, to convert the original data to KML. Our KML generator accepts the research data such as navigation data, sea water salinity and temperature data (CTD data), geomagnetic field data, and bathymetry data obtained in research vessels. The KML generator enables us to visualize those data on Google Earth quickly and compare with other data easily. It would become a powerful tool to interpret these research data and to get insights toward Earth's dynamical processes.

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Real-time monitoring of broadband seismographs through the Internet enables us to discover various technical troubles of broadband seismic observation system of Pacific21 and to take measures to solve them at the next field maintenance occasions. This paper summarizes the characteristics and the countermeasures of four typical troubles that we discovered from real-time monitoring or encountered in our maintenance work. One trouble was a deviation of seismometer's response owing to insufficient insulation of its connector. It was very effective to protect the connectors from moisture as a preventive measure. Another trouble was that spike-like noise was generated in the seismometer's output when some equipment demanded high current from the power supply. In order to remove the noises, we have two solutions: to disconnect extra impedance from the grounding line for power return, and to improve the power supply. A third was high frequency noise from one-sided connection of differential signaling. It is important to check the waveforms diligently to find this trouble as soon as possible. The other was that the data logger's dedicated hard disk often stopped for a maximum of several hours. The frequency of bard disk's shutdown seems to depend on its firmware version. For this trouble, we learned that we should operate equipment with various firmware versions for some time before installation.

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Global seismic network is one of the powerful means for research of earth interior's dynamics. IFREE install and operate broadband seismic network in western pacific region. For the purpose of recording high quality data, station should be operated stably without any suspensions. IFREE upgraded the recording system and installed IP communication line for latest five years. Therefore we constructed real time data archive and station's status monitoring systems. The rate of operation is much higher due to upgrade to telemeter station than off line recording period. It is realized that full length seismic data set is archived with minimum interruption.

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This paper briefly explains a recently developed numerical technique called PDS-FEM and its dynamic extension. PDS-FEM is a simple and efficient numerical technique for modeling propagation crack in brittle materials. The discretization scheme used in this new numerical technique is called particle discretization scheme (PDS). PDS uses characteristic functions of Voronoi and Delaunay tessellations to discretize function and its derivatives, respectively. The uses of non-overlapping shape functions facilitate simple and numerically efficient failure treatment. We considered the dynamic extension of PDS-FEM and simulated several real life experiments, to illustrate the potential of simulating dynamic crack propagation of problems requiring fine domain discretizations.

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Hyper Intelligent Discrete Element Method (HiDEM), developed by the crustal dynamics research group, Institute for Research and Earth Evolution (IFREE), Japan Agency for Marine-Earth Science and Technology (JAMSTEC) is introduced together with its algorithm and its high speed computational programming technique. In addition, the contribution of HiDEM for research and development in science and industry is mentioned introducing some examples.

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The wide-angle seismic reflection/refraction data analyses play important roles in determining lithospheric scale crustal structures and understanding tectonic processes in the lithosphere. The structure analysis is an intrinsically nonlinear and often an underdetermined problem. Therefore, several subjective analysis processes are usually required for modeling lithospheric scale structure. Generally, subjective analysis processes reduce the credibility of the resultant models and we cannot discuss fine variation of the obtained structure models. Recently, the increasing the quality and quantity of the seismic data as well as the increasing the computer power has enabled us to apply advanced and objective structure analysis approaches and to discuss the detailed structure variation. In this paper, I show my developed and adopted structure analysis approaches and software tools for constructing the lithospheric scale crustal structure models objectively.

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