Scientific Drilling Program of Drilling Vessel Chikyu and Drilling Data Acquisition for Future Technical Development

2011 ◽  
Author(s):  
Tomoya Inoue ◽  
Kazuyasu Wada ◽  
Eigo Miyazaki ◽  
Tsuyoshi Miyazaki
Keyword(s):  
Data Acquisition ◽  
Subduction Zones ◽  
Large Scale ◽  
Nankai Trough ◽  
Technical Development ◽  
Seismogenic Zone ◽  
Validity Data ◽  
Scientific Drilling ◽  
Drilling Data ◽  
Drilling Operations

The scientific drilling vessel Chikyu has started drilling at Nankai trough under the international organization, IODP. The Nankai trough located beneath the ocean off the southwest coast of Japan is one of the most active earthquake zones on the planet and one of the best-studied subduction zones as well. The Nankai Trough Seismogenic Zone Experiment attempts for the first time to drill, sample, and instrument the earthquake-causing or the seismogenic portion of Earth’s crust, where violent, large-scale earthquakes have occurred repeatedly throughout history. Before starting the international drilling operations, an integration drilling test off Shimokita Peninsula was conducted and we acquired actual drilling data such as vessel heave, hook load, and compensator position. Confirming its validity, data acquisition systems have worked continuously in international drilling operations. It is very important to consider the actual drilling data for the drilling operation and for further technical development. This paper describes the scientific drilling programs of the drilling vessel Chikyu and the drilling data acquisition for future technical development in relation with the sample data acquired in the internal drilling operations.

Effect of Drill-Ship Motions on Core Sample Conditions During the Nankai Trough Seismogenic Zone Experiment

2009 ◽  
Author(s):  
Yuichi Shinmoto ◽  
Kazuyasu Wada
Keyword(s):  
Deep Sea ◽  
Nankai Trough ◽  
Drill String ◽  
Seismogenic Zone ◽  
Ship Motions ◽  
Scientific Drilling ◽  
Core Samples ◽  
Core Recovery ◽  
Drilling Parameters ◽  
Core Conditions

The Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) Stage 1A, which is a part of the Integrated Ocean Drilling Program (IODP), is a series of expeditions in scientific drilling and coring operations aboard the first riser-equipped deep sea drilling vessel, Chikyu. The objectives are to recover good quality core samples and collect data on undersea properties and drilling conditions, which will also provide valuable information for future expeditions. The coring operations were carried out under harsh drilling and ocean conditions so that core recovery was inconsistent and fluctuated from high to low. Moreover, differences in independent lithology, depth, and the type of coring tools from previous expeditions made it necessary to analyze and optimize drilling parameters with new data. A serious concern in retrieving core samples was the vertical heave motions caused by the drill-ship since the active heave compensator system could not be activated before operations due to the extreme deep sea conditions and only the passive heave compensator was used. The drill string and coring tools are particularly vulnerable to the high heaving movements of the vessel so that the core recovery rate and quality are also adversely affected. The present work presents an analysis of geotechnical information, drilling parameters and the drill-ship motions the NanTroSEIZE expedition in order to optimize core conditions and maintain high core recovery.

scholarly journals Structural Research on the Nankai Trough Using Reflections and Refractions

2009 ◽  
Vol 4 (2) ◽  
pp. 67-71 ◽  
Author(s):  
Yoshiyuki Kaneda ◽  
◽  
Shuichi Kodaira
Keyword(s):  
Large Scale ◽  
Nankai Trough ◽  
Disaster Mitigation ◽  
Seismic Survey ◽  
Seismogenic Zone ◽  
Significant Information ◽  
Megathrust Earthquake ◽  
Megathrust Earthquakes ◽  
Recurrence System ◽  
Splay Faults

To understand the megathrusut earthquake recurrence system around the Nankai trough southwestern Japan, the structural researches by seismic survey and observations will provide the significant information of megathrust earthquakes seimogenic zone. As previous structural researches, the subducting seamount in the Nankai earthquake seismogenic zone off Shikoku Island, the ridge subducting system in the Tokai earthquake seismogenic zone, splay faults in the Tonankai earthquake seismogenic zone and irregular structure in the boundary between the Tonankai and Nankai seismogenic zone off Kii peninsula.These structures and models are very important, significant and basical information to understand the recurrence system of megathrust earthquakes and rupture propagations.In this project, we will carry out seismic survey and tomography with dense arrays around the Nankai trough extending to off Hyuga sesimogenic zone. By 2004 Sumatra megathrust earthquake, we recognized such the large scale seismic linkage as 1960 Chile megathrust earthquake.Therefore, we will image large detailed large scale structures to understand structural components around the Nankai trough with off Hyuga area. Finally, we will construct the advanced structure model and develop the crustal medium model in close cooperation with other structural researches in this project. Based on these models, simulation and disaster mitigation researches will progress conspicuously.

Recent advances in GNSS-A observation technology and networks and latest observation results around Japan Islands

2020 ◽  
Author(s):  
Yusuke Yokota ◽  
Tadashi Ishikawa ◽  
Shun-ichi Watanabe ◽  
Yuto Nakamura
Keyword(s):  
Subduction Zones ◽  
Large Scale ◽  
Surface Deformation ◽  
Nankai Trough ◽  
Detection Sensitivity ◽  
Japan Trench ◽  
Observation Data ◽  
Coupling Condition ◽  
Slow Slip Events ◽  
Combination Technique

<p>Our research group has been studying advanced GNSS-A (Global Navigation Satellite System – Acoustic ranging combination) technique over two decades. In recent years, detection sensitivity of GNSS-A observations has been sophisticated by improving the accuracy and frequency of analysis technology and acoustic systems [e.g., Yokota et al., 2018, MGR; Ishikawa et al., in prep]. The current observation frequency is more than 4 times/year, the observation accuracy for each observation is less than 2 cm, and it can detect a steady deformation rate of 1 cm/year or less and an unsteady fluctuation of 5 cm or less. Also, efforts are being made to strengthen the observation network.</p><p>GNSS-A observations for the 2011 Tohoku-oki earthquake and its postseismic field revealed the details of the crustal deformation field on the Japan Trench side [Sato et al., 2011, Science; Watanabe et al., 2014, GRL]. The long-term observation data in the Nankai Trough region revealed the strain accumulation process at the interseismic period [Yokota et al., 2016, Nature; Watanabe et al., 2018, JGR; Nishimura et al., 2018, Geosphere]. Furthermore, detection and monitoring of large-scale slow slip events (SSEs) in the shallow part of the Nankai Trough was achieved by recent sensitivity improvements [Yokota & Ishikawa, 2020, Science Advances]. The detected postseismic fields, coupling condition and shallow SSEs contain universal features that should be shared in many subduction zones. Here, along with the latest observations, we discuss spatial and temporal relationships of these events, strain accumulations and releases along subduction zones around Japan by GNSS-A and its impact on slow earthquake science.</p><p>Recently, because of the need for continuous monitoring a shallow SSE, the monitoring ability of GNSS-A was also investigated. It was confirmed that relatively large-scale shallow SSE (surface deformation: > 5 cm) could be monitored. However, the ability to determine the time constant of an SSE is poor. For monitoring the detail of an SSE, it is essential to improve the observation frequency in the future. Here, we also discuss the technical issues to be considered and their solution plans (e.g., new platform and system).</p>

Drill String Strength Evaluation for Deep Earthquake Zone Drilling

2012 ◽  
Author(s):  
Tomoya Inoue ◽  
Masanori Kyo ◽  
Koji Sakura ◽  
Toshihiko Fukui
Keyword(s):  
Nankai Trough ◽  
Drill Pipe ◽  
High Strength ◽  
Seismogenic Zone ◽  
Deep Drilling ◽  
Deep Earthquake ◽  
Strength Evaluation ◽  
Scientific Drilling ◽  
Drill Pipes ◽  
Earthquake Zone

The scientific drilling vessel Chikyu was designed to have the deep drilling capability to reach the deep earthquake zone. To realize such deep drilling, a drill pipe with higher than ever strength and reliability is of necessity. A strength evaluation of such high strength drill pipe is also necessary. Around Japan, the earthquake zones are widely located under the seabed in deep water. For example, the Nankai Trough located beneath the ocean off the southwest coast of Japan is one of the most active earthquake zones where large-scale earthquakes have occurred repeatedly throughout history. Thus, the Chikyu has started the first scientific drilling at the Nankai Trough as the Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE). NanTroSEIZE targets the megasplay fault zone at 3500 m below the seafloor and finally 6000m deep drilling into the seismogenic zone and across the plate interface into the subducting crust at water depths of around 2500m. In addition, a huge earthquake zone is expected to be located about 1000m below the seafloor at water depths of around 7000m. For this drilling task, the riserless drilling technique should be applied. To realize such deep drilling with both riser and riserless techniques, a S150 drill pipe was developed during the construction phase and has been used in the past scientific drillings of the Chikyu. For deeper drillings in the future and drilling operations in harsh environments, we are developing superior high strength drill pipes, S155 and S160, possessing high reliability including corrosion resistance to achieve high toughness and reduction of stress concentration. An evaluation of the maximum possible stress was conducted. In the maximum strength evaluation, we considered dynamic stress and bending stress due to the current and the vessel inclination. This paper describes the development of superior high strength drill pipes and the strength evaluation of such drill pipes for deep earthquake zone drilling.

scholarly journals IODP workshop: Core-Log Seismic Investigation at Sea – Integrating legacy data to address outstanding research questions in the Nankai Trough Seismogenic Zone Experiment

2018 ◽  
Vol 24 ◽  
pp. 93-107
Author(s):  
Anna Cerchiari ◽  
Rina Fukuchi ◽  
Baiyuan Gao ◽  
Kan-Hsi Hsiung ◽  
Dominik Jaeger ◽  
...  
Keyword(s):  
Subduction Zone ◽  
Seismic Data ◽  
Subduction Zones ◽  
Nankai Trough ◽  
Early Career ◽  
Seismogenic Zone ◽  
Geochemical Data ◽  
Deformation Front ◽  
Subduction Zone Processes ◽  
Research Questions

Abstract. The first International Ocean Discovery Program (IODP) Core-Log-Seismic Integration at Sea (CLSI@Sea) workshop, held in January–February 2018, brought together an international, multidisciplinary team of 14 early-career scientists and a group of scientific mentors specialized in subduction zone processes at the Nankai Trough, one of the Earth's most active plate-subduction zones located off the southwestern coast of Japan. The goal of the workshop was to leverage existing core, log, and seismic data previously acquired during the IODP's Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE), to address the role of the deformation front of the Nankai accretionary prism in tsunamigenic earthquakes and slow slip in the shallow portion of the subduction interface. The CLSI@Sea workshop was organized onboard the D/V Chikyu concurrently with IODP Expedition 380, allowing workshop participants to interact with expedition scientists installing a long-term borehole monitoring system (LTBMS) at a site where the workshop's research was focused. Sedimentary cores from across the deformation front were brought onboard Chikyu, where they were made available for new description, sampling, and analysis. Logging data, drilling parameters, and seismic data were also available for investigation by workshop participants, who were granted access to Chikyu laboratory facilities and software to perform analyses at sea. Multi-thematic presentations facilitated knowledge transfer between the participants across field areas, and highlighted the value of multi-disciplinary collaboration that integrates processes across different spatiotemporal scales. The workshop resulted in the synthesis of existing geophysical, geologic, and geochemical data spanning IODP Sites C0006, C0007, C0011 and C0012 in the NanTroSEIZE area, the identification of key outstanding research questions in the field of shallow subduction zone seismogenesis, and fostered collaborative and individual research plans integrating new data analysis techniques and multidisciplinary approaches.

Investigating seismic segmentation and recurrence patterns of great earthquakes along the Chilean megathrust.

2020 ◽  
Author(s):  
Diego Molina ◽  
Andres Tassara ◽  
Jean-Paul Ampuero ◽  
Daniel Melnick
Keyword(s):  
Subduction Zones ◽  
Large Scale ◽  
Seismogenic Zone ◽  
Recurrence Time ◽  
Small Scale ◽  
Apparent Difference ◽  
Coseismic Slip ◽  
First Order ◽  
Megathrust Earthquakes ◽  
Chilean Margin

<p>Megathrust earthquakes at subduction zones are one of the most devastating natural phenomena. Understanding the relationships between their temporal recurrence, spatial segmentation and the frictional structure of the megathrust is of primary relevance. We analyzed the common spatial variability of gravity anomalies, geodetic locking and wedge taper basal friction (three independent proxies for megathrust frictional structure) along the Chilean margin. A marked along-strike segmentation has emerged that is organized into three hierarchical levels. At a subcontinental-scale (10<sup>3</sup> km), we observe a first-order difference between Central (18-32°S) and Southern (32°-46°S) Andes. This is marked by a dominance of positive/negative gravity, high/low locking, high/low friction along the Central/Southern segments. We explain this as mainly reflecting the combined effect on effective normal stress (σ<sub>eff</sub>) of a high/low density forearc and low/high pore pressure along both megathrust segments, in agreement with the geological structure of the forearc, sediment input at the trench and the long-term architecture of the Andes. Inside this large-scale subdivision, we identify a number of segments (10<sup>2</sup> km) that are limited by marked small-scale (10<sup>1</sup> km) changes in the first-order tendency of the three proxies coinciding with geological features of both plates. When we compare this against the paleoseismic, historic and instrumental record of past earthquakes in Chile, we note that segments largely coincide with seismic asperities, i.e. those regions of the megathrust concentrating the largest fraction of coseismic slip. Bridging these two scales, the rupture length of giant (Mw 8.5-9.5) earthquakes, which encompassed several asperities, define an intermediate hierarchic level of organization (10<sup>2</sup>-10<sup>3</sup> km). Considering this segmentation into the conceptual framework of the rate-and-state friction (RSF) law, we infer that asperities inside the rate-weakening seismogenic zone of the Central Andean megathrust are dominantly unstable (i.e. σ<sub>eff</sub>>σ<sub>c</sub> = the critical stress defined by RSF parameters) and therefore prone to initiate and concentrate the coseismic rupture. In contrast, most of the asperities along the Southern mega-segment are likely characterized by a conditionally-stable behavior (σ<sub>eff</sub><σ<sub>c</sub>) that allows a rich and complex seismogenic behavior where interseismic creep and locking are both possible and large coseismic slip propagation is dominant. This can explain the apparent difference in the recurrence of giant earthquakes along both mega-segments, since the synchronization of unstable asperities in the Central Andean megathrust (2000-3000 yr recurrence time) is less probable than in the case of conditionally-stable asperities in the Southern segment (300-500 yrs). We will test these hypothesis developing numerical simulations of multiple seismic cycles with setups representing the inferred contrast on the physical properties of the megathrust along the Chilean margin, and we will present preliminary results of this exercise. </p>

Overdeepened glacial basins as archives for Pleistocene glaciation history and subglacial processes: Results from scientific drilling in the Northern Alpine Foreland

2020 ◽  
Author(s):  
Marius W. Buechi ◽  
Gaudenz Deplazes ◽  
Lukas Gegg ◽  
Herfried Madritsch ◽  
Flavio S. Anselmetti
Keyword(s):  
Large Scale ◽  
Geophysical Methods ◽  
Pleistocene Glaciation ◽  
Scientific Drilling ◽  
Northern Switzerland ◽  
Quaternary Glaciation ◽  
History Of ◽  
Drilling Operations ◽  
The Alps ◽  
Multi Method Approach

<p>Overdeepened glacial basins are excellent archives for the Quaternary glaciation history and the landscape evolution of the Alps. While they are common large-scale glacial features in many inner-Alpine and foreland settings, most of these basins remain underexplored as challenging drilling operations into 10s to 100s of meters of unconsolidated sediment are required to access the sedimentary record.</p><p>We currently investigate some of the most prominent overdeepened glacial basins between the Aare and Rhine Rivers in Northern Switzerland with a multi-method approach –  including geophysical methods and scientific drilling – to characterise the geometry, sedimentary infill and age of these glacial basins. The focus of this research is on 1) extracting and refining the Middle to Late Pleistocene glaciation history of Northern Switzerland, and 2) identifying the mechanisms and controls of overdeepening subglacial erosion by characterizing former ice-contacts in the basin fills using micro- to macroscale sedimentological tools.</p>

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