4. Solid earth sciences

The Atlantis Bank Gabbro Massif, Southwest Indian Ridge

This paper presents the first detailed geologic map of in situ lower ocean crust; the product of six surveys of Atlantis Bank on the SW Indian Ridge. This combined with major and trace element compositions of ...

Authors: Henry J. B. Dick, Astri J. S. Kvassnes, Paul T. Robinson, Christopher J. MacLeod and Hajimu Kinoshita

Assessment of directional accuracy of GNSS-Acoustic measurement using a slackly moored buoy

We assessed the positioning accuracy of GNSS-Acoustic (GNSS-A) measurement using a slackly moored buoy. A key feature of real-time buoy-based GNSS-A measurement is that positioning must be performed via single...

Authors: Misae Imano, Motoyuki Kido, Chie Honsho, Yusaku Ohta, Narumi Takahashi, Tatsuya Fukuda, Hiroshi Ochi and Ryota Hino

Some remarks on hydrogen-assisted electrical conductivity in olivine and other minerals

Electrical conductivity in minerals is sensitive to hydrogen content, and therefore, it is a potentially important property from which one can infer hydrogen (water) distribution in the mantle. However, there ...

Authors: Shun-ichiro Karato

Sensitivity of elastic thickness to water in the Martian lithosphere

Ancient Mars likely hosted oceans similar to those on Earth; however, such water is not presently observed on Mars. One possible explanation for the lack of present-day oceans is that surface water was transpo...

Authors: Ikuo Katayama, Yuhki Matsuoka and Shintaro Azuma

Effects of frictional properties of quartz and feldspar in the crust on the depth extent of the seismogenic zone

The depth extent of the crustal seismogenic zone is closely related to the size of earthquakes. The mechanisms that control the depth of the lower transition of the seismogenic zone are important issues in sei...

Authors: Koji Masuda, Takashi Arai and Miki Takahashi

Significant P wave conversions from upgoing S waves generated by very deep earthquakes around Japan

An important component of the seismic wavefield at moderate epicentral distances from deep earthquakes comes from seismic waves that are radiated upwards from the source. For very deep events, there is a range...

Authors: B. L. N. Kennett and T. Furumura

Detection of repeating earthquakes and their application in characterizing slow fault slip

Repeating earthquakes (repeaters) that rupture the same fault area (patch) are interpreted to be caused by repeated accumulation and release of stress on the seismic patch in a creeping area. This relationship...

Authors: Naoki Uchida

Nitrogen in the Earth: abundance and transport

The terrestrial nitrogen budget, distribution, and evolution are governed by biological and geological recycling. The biological cycle provides the nitrogen input for the geological cycle, which, in turn, feed...

Authors: Bjorn Mysen

Postseismic fluid discharge chemically recorded in altered pseudotachylyte discovered from an ancient megasplay fault: an example from the Nobeoka Thrust in the Shimanto accretionary complex, SW Japan

Megasplay fault branching from plate boundaries of subduction zones is thought to be important sources of earthquakes and tsunamis. In this study, we performed structural and geochemical analyses on a fossiliz...

Authors: Ryota Hasegawa, Asuka Yamaguchi, Rina Fukuchi, Yohei Hamada, Nobuhiro Ogawa, Yujin Kitamura, Gaku Kimura, Juichiro Ashi and Tsuyoshi Ishikawa

The architecture of long-lived fault zones: insights from microstructure and quartz lattice-preferred orientations in mylonites of the Median Tectonic Line, SW Japan

We combine field mapping with quartz microstructure and lattice preferred orientations (LPO) to constrain the mechanisms and spatio-temporal distribution of deformation surrounding the Median Tectonic Line (MT...

Authors: Thomas A. Czertowicz, Toru Takeshita, Shun Arai, Takafumi Yamamoto, Jun-Ichi Ando, Norio Shigematsu and Ko-Ichiro Fujimoto

Drastic effect of shearing on graphite microtexture: attention and application to Earth science

The microtexture of graphite exposed on the polished surface was studied using confocal laser scanning microscopy, laser Raman spectroscopy, and focused ion beam–transmission electron microscopy (FIB–TEM) to e...

Authors: Yui Kouketsu, Akira Miyake, Yohei Igami, Tomoki Taguchi, Hiroyuki Kagi and Masaki Enami

Thermal maturity structures in an accretionary wedge by a numerical simulation

This study investigates the thermal maturity structure of the accretionary wedge along with the thermal history of sediments during wedge formation using a numerical simulation. The thermal maturity, which is ...

Authors: Ayumu Miyakawa, Masataka Kinoshita, Yohei Hamada and Makoto Otsubo

Geometrical dependence on the stress and slip tendency acting on the subduction megathrust of the Nankai seismogenic zone off Kumano

We assess the dependence of megathrust geometry near the updip edge of the Nankai seismogenic zone according to the slip tendency of the megathrust based on a reprocessed 3D PSDM seismic volume image and Inter...

Authors: Masataka Kinoshita, Kazuya Shiraishi, Evi Demetriou, Yoshitaka Hashimoto and Weiren Lin

Pliocene integrated chronostratigraphy from the Anno Formation, Awa Group, Boso Peninsula, central Japan, and its paleoceanographic implications

The Pliocene climate is one of the best analogs for the climate of a globally warmer future. Here, we present a new Pliocene integrated chronostratigraphy from the Anno Formation in the uppermost Awa Group, wh...

Authors: Yuki Haneda and Makoto Okada

Estimate of the contraction rate of central Japan through the deformation of the Philippine Sea slab

The Philippine Sea (PHS) slab is severely deformed beneath central Japan, but it is subject to little deformation before the subduction along the Nankai Trough. Thus, it is considered that the currently observ...

Authors: Yukitoshi Fukahata

Paleo-stress orientations and magnitudes from triaxial testing and stress inversion analysis in Nankai accretionary prism sediments

Combined knowledge on the magnitude as well as the orientation of paleo-stress is usually not given. Based on drilling investigations and laboratory experiments, we are able to provide both, constraints on pal...

Authors: Yoshitaka Hashimoto, Michael Stipp, Jonathan C. Lewis and Frank Wuttke

Spatio-temporal changes in the seismic velocity induced by the 2011 Tohoku-Oki earthquake and slow slip event revealed from seismic interferometry, using ocean bottom seismometer’s records

Seismic interferometry is one of the most effective techniques for detecting temporal variations in seismic velocity caused by large earthquakes. Before the 2011 Tohoku-Oki earthquake (M_w9.0) near the Japan Trenc...

Authors: Miyuu Uemura, Yoshihiro Ito, Kazuaki Ohta, Ryota Hino and Masanao Shinohara

Mantle-derived fluids in the Nankai Trough Kumano forearc basin

Noble gas abundance and isotope data from 12 drilling mud gas samples obtained during IODP Expeditions 338 and 348 provide new insights on fluid origin and fluid migration in the inner accretionary prism below...

Authors: Thomas Wiersberg, Sebastian B. Hammerschmidt, Shigeshi Fuchida, Achim Kopf and Jörg Erzinger

Punctuated growth of an accretionary prism and the onset of a seismogenic megathrust in the Nankai Trough

Ocean drilling in the Nankai Trough forearc suggests a new scenario for the evolution of the Nankai subduction zone. Continuous subduction since the Late Cretaceous has been a common tectonic scenario, althoug...

Authors: Gaku Kimura, Hiroaki Koge and Takeshi Tsuji

In-situ mechanical weakness of subducting sediments beneath a plate boundary décollement in the Nankai Trough

The study investigates the in-situ strength of sediments across a plate boundary décollement using drilling parameters recorded when a 1180-m-deep borehole was established during International Ocean Discovery ...

Authors: Yohei Hamada, Takehiro Hirose, Akira Ijiri, Yasuhiro Yamada, Yoshinori Sanada, Saneatsu Saito, Noriaki Sakurai, Takamitsu Sugihara, Takahiro Yokoyama, Tomokazu Saruhashi, Tatsuhiko Hoshino, Nana Kamiya, Stephen Bowden, Margaret Cramm, Susann Henkel, Kira Homola…

Dynamic formation process of thick deformation zone on the shallow plate boundary fault of the Japan Trench: insight from analog experiments of half-graben subduction

The 2011 Tohoku-oki earthquake unexpectedly ruptured to the shallowest portion of the plate boundary fault and triggered a large tsunami. The shallow portion had generally been regarded as a seismically stable...

Authors: Hiroaki Koge, Yasuhiro Yamada, Akihiro Ohde, Arthur Bauville, Asuka Yamaguchi and Juichiro Ashi

Three-dimensional mapping and kinematic characterization of mass transport deposits along the outer Kumano Basin and Nankai accretionary wedge, southwest Japan

Three-dimensional (3D) seismic data from the southern Kumano Basin of southwest Japan image a nested series of moderately sized mass transport deposits (MTDs) that slid from a slope along the seaward side of t...

Authors: Jason Lackey, Gregory Moore and Michael Strasser

Earthquake early warning: what does “seconds before a strong hit” mean?

An earthquake early warning (EEW) system is designed to detect an event, determine its parameters (hypocenter, magnitude, and origin time), and issue an alert to sites/areas where necessary actions should be t...

Authors: Fumiko Tajima and Takumi Hayashida

Temporal change in seismic velocity associated with an offshore M_W 5.9 Off-Mie earthquake in the Nankai subduction zone from ambient noise cross-correlation

The Nankai subduction zone off the Kii Peninsula, Japan, has a large potential to generate megathrust earthquakes in the near future. To investigate the temporal variation of stress or strain in the Nankai sub...

Authors: Tatsunori Ikeda and Takeshi Tsuji

Surface deformation and source modeling of Ayaz-Akhtarma mud volcano, Azerbaijan, as detected by ALOS/ALOS-2 InSAR

Azerbaijan, located on the western edge of the Caspian Sea in Central Asia, has one of the highest populations of mud volcanoes in the world. We used satellite-based synthetic aperture radar (SAR) images deriv...

Authors: Kento Iio and Masato Furuya

Temporal changes in the internal stresses and pore pressures in a large-scale submarine mass transport deposit

We examined the temporal changes in the internal stresses and pore fluid pressures of a submarine mass transport deposit (MTD) in the Akkeshi Formation of the Upper Cretaceous–Paleocene Nemuro Group, eastern H...

Authors: Makoto Otsubo, Hajime Naruse and Ayumu Miyakawa

On the evolution of the water ocean in the plate-mantle system

Here, we investigate a possible scenario of surface seawater evolution in the numerical simulations of surface plate motion driven by mantle dynamics, including thermo-chemical convection and water migration, ...

Authors: Takashi Nakagawa, Hikaru Iwamori, Ryunosuke Yanagi and Atsushi Nakao

Development of a database and visualization system integrating various models of seismic velocity structure and subducting plate geometry around Japan

To estimate strong ground motions caused by future earthquakes in Japan and to more accurately predict seismic hazards and tsunamis, it is necessary to accurately model the geometry of the subducting plate and...

Authors: Yasuko Yamagishi, Ayako Nakanishi, Seiichi Miura, Shuichi Kodaira and Hide Sakaguchi

Redox-controlled mechanisms of C and H isotope fractionation between silicate melt and COH fluid in the Earth’s interior

The behavior of COH fluids, their isotopes (hydrogen and carbon), and their interaction with magmatic liquids are at the core of understanding formation and evolution of the Earth. Experimental data are needed...

Authors: Bjorn Mysen

High-density surveys conducted to reveal active deformations of the upper forearc slope along the Ryukyu Trench, western Pacific, Japan

In this study, which was conducted to investigate present-day geological deformations occurring off the central Ryukyu Arc along the Ryukyu Trench (Okinawa-jima) in the vicinity of Japan, we obtained and exami...

Authors: Kohsaku Arai, Takahiko Inoue and Tomoyuki Sato

Variations in precursory slip behavior resulting from frictional heterogeneity

Precursory seismicity is often observed before a large earthquake. Small foreshocks occur within the mainshock rupture area, which cannot be explained by simple models that assume homogeneous friction on the e...

Authors: Suguru Yabe and Satoshi Ide

Silicate solution, cation properties, and mass transfer by aqueous fluid in the Earth’s interior

Aqueous fluids in the Earth’s interior are multicomponent systems with silicate solubility and solution mechanisms strongly dependent on other dissolved components. Here, solution mechanisms that describe the ...

Authors: Bjorn Mysen

Nonlinear dynamical analysis of GNSS data: quantification, precursors and synchronisation

The goal of any nonlinear dynamical analysis of a data series is to extract features of the dynamics of the underlying physical and chemical processes that produce that spatial pattern or time series; a by-pro...

Authors: Bruce Hobbs and Alison Ord

What causes subsidence following the 2011 eruption at Nabro (Eritrea)?

A major goal in volcanology is to be able to constrain the physical properties of a volcanic system using surface observations. The behaviour of a volcanic system following an eruption can provide powerful con...

Authors: Joanna Hamlyn, Tim Wright, Richard Walters, Carolina Pagli, Eugenio Sansosti, Francesco Casu, Susi Pepe, Marie Edmonds, Brendan McCormick Kilbride, Derek Keir, Jürgen Neuberg and Clive Oppenheimer

The 2016 M_w 5.9 earthquake off the southeastern coast of Mie Prefecture as an indicator of preparatory processes of the next Nankai Trough megathrust earthquake

Megathrust earthquakes have occurred repeatedly at intervals of 100 to 150 years along the Nankai Trough, situated in the southwest of Japan. Given that it has been 70 years since the last event, the occurrenc...

Authors: Masaru Nakano, Mamoru Hyodo, Ayako Nakanishi, Mikiya Yamashita, Takane Hori, Shin-ichiro Kamiya, Kensuke Suzuki, Takashi Tonegawa, Shuichi Kodaira, Narumi Takahashi and Yoshiyuki Kaneda

Rheology and stress in subduction zones around the aseismic/seismic transition

Subduction channels are commonly occupied by deformed and metamorphosed basaltic rocks, together with clastic and pelagic sediments, which form a zone up to several kilometers thick to depths of at least 40 km...

Authors: John P. Platt, Haoran Xia and William Lamborn Schmidt

Deep magnetic field stretching in numerical dynamos

The process of magnetic field stretching transfers kinetic energy to magnetic energy and thereby maintains dynamos against ohmic dissipation. Stretching at depth may play an important role in shaping the field...

Authors: Diego Peña, Hagay Amit and Katia J. Pinheiro

Reconstruction of sediment-transport pathways on a modern microtidal coast by a new grain-size trend analysis method

A new method for granulometric-parameter-based reconstruction of sediment-transport pathways is proposed and is termed P-GSTA (grain-size trend analysis using principal component analysis) herein. The main adv...

Authors: Shota Yamashita, Hajime Naruse and Takeshi Nakajo

Mass transfer in the Earth’s interior: fluid-melt interaction in aluminosilicate–C–O–H–N systems at high pressure and temperature under oxidizing conditions

Understanding what governs the speciation in the C–O–H–N system aids our knowledge of how volatiles affect mass transfer processes in the Earth’s interior. Experiments with aluminosilicate melt + C–O–H–N volat...

Authors: Bjorn Mysen

Spatial pattern in stress drops of moderate-sized earthquakes on the Pacific Plate off the south-east of Hokkaido, Japan: implications for the heterogeneity of frictional properties

We show that the spatial heterogeneity in the coseismic displacement of large earthquakes likely reflects the spatial characteristics of the frictional properties and that it can be inferred from the stress dr...

Authors: Takuji Yamada, Yu Saito, Yuichiro Tanioka and Jun Kawahara

Melting phase relations in the MgSiO₃–CaSiO₃ system at 24 GPa

The Earth’s lower mantle is composed of bridgmanite, ferropericlase, and CaSiO₃-rich perovskite. The melting phase relations between each component are key to understanding the melting of the Earth’s lower mantle...

Authors: Ryuichi Nomura, Youmo Zhou and Tetsuo Irifune

Adjoint tomography of the crust and upper mantle structure beneath the Kanto region using broadband seismograms

A three-dimensional seismic wave speed model in the Kanto region of Japan was developed using adjoint tomography for application in the effective reproduction of observed waveforms. Starting with a model based...

Authors: Takayuki Miyoshi, Masayuki Obayashi, Daniel Peter, Yoko Tono and Seiji Tsuboi

Possible climate preconditioning on submarine landslides along a convergent margin, Nankai Trough (NE Pacific)

Submarine landslides are major agents of sediment mass transfer from the shallow to deep sea. Due to their rapid emplacement and tsunamigenic potential, such landslides are significant geohazards for society a...

Authors: Katrina Kremer, Muhammed O. Usman, Yasufumi Satoguchi, Yoshitaka Nagahashi, Sunil Vadakkepuliyambatta, Giuliana Panieri and Michael Strasser

Structural context and variation of ocean plate stratigraphy, Franciscan Complex, California: insight into mélange origins and subduction-accretion processes

The transfer (accretion) of materials from a subducting oceanic plate to a subduction-accretionary complex has produced rock assemblages recording the history of the subducted oceanic plate from formation to a...

Authors: John Wakabayashi

The responses of the four main substitution mechanisms of H in olivine to H₂O activity at 1050 °C and 3 GPa

Authors: Peter M. E. Tollan, Rachel Smith, Hugh St.C. O’Neill and Jörg Hermann

Seismic imaging of slab metamorphism and genesis of intermediate-depth intraslab earthquakes

We review studies of intermediate-depth seismicity and seismic imaging of the interior of subducting slabs in relation to slab metamorphism and their implications for the genesis of intermediate-depth earthqua...

Authors: Akira Hasegawa and Junichi Nakajima

Melting relations in the Fe–S–Si system at high pressure and temperature: implications for the planetary core

The phase and melting relations in the Fe–S–Si system were determined up to 60 GPa by using a double-sided laser-heated diamond anvil cell combined with X-ray diffraction. On the basis of the X-ray diffraction...

Authors: Takanori Sakairi, Eiji Ohtani, Seiji Kamada, Takeshi Sakai, Tatsuya Sakamaki and Naohisa Hirao

Hydrogen mobility in transition zone silicates

We study the hydrogen mobility in ringwoodite and wadsleyite considering multiple charge-balanced defects, including Mg < = > 2H, Si < = > Mg + 2H, and the hydrogarnet defect, Si < = > 4H, using molecular dyna...

Authors: Razvan Caracas and Wendy R. Panero

A numerical shallow-water model for gravity currents for a wide range of density differences

Gravity currents with various contrasting densities play a role in mass transport in a number of geophysical situations. The ratio of the density of the current, ρ _c, to the density of the...

Authors: Hiroyuki A. Shimizu, Takehiro Koyaguchi and Yujiro J. Suzuki

Interplay of irreversible reactions and deformation: a case of hydrofracturing in the rodingite–serpentinite system

The interplay of irreversible reactions and deformation during regional metamorphism was analyzed in the reaction zones between rodingite and serpentinite. Rodingites are leucocratic rocks found commonly in se...

Authors: Tadao Nishiyama, Chisato Yoshida- Shiosaki, Yasushi Mori and Miki Shigeno