Investigating the role of the Itoigawa-Shizuoka tectonic line towards the evolution of the Northern Fossa Magna rift basin

AbstractThe Itoigawa-Shizuoka tectonic line (ISTL) fault system is considered to have one of the highest probabilities for a major inland earthquake occurrence in the whole of Japan. It is a complex fault system with the dip directions of the local fault segments changing from north to south between an east-dipping low-angle thrust fault, a strike slip fault and a west-dipping thrust fault. The tectonic relations between the different parts of the fault system and the surrounding geological units are yet to be fully explained. This study aims to reveal the juncture of the northern and central parts of the ISTL and investigate its contribution towards the shaping of the Northern Fossa Magna rift basin. We conducted 3 deployments of 1 or 2 linear arrays of seismic stations across the central and northern ISTL regions and observed local micro-earthquakes for a period of 3 years. Each deployment recorded continuous waveform data for approximately 3 months. Using arrival times of 1193 local earthquakes, we jointly determined earthquake locations and a 3D velocity model, applying the tomography method. We were able to image the regional crustal structures from the surface to a depth of 20km with a spatial resolution of 5km. Subsequently, we used the obtained 3D velocity model to relocate the background local seismicity from 2003 to 2009. The juncture of the northern and central parts of the ISTL was well constrained by our results. The depth extension of the northern parts of the ISTL fault segments follows the bottom of the Miocene Northern Fossa Magna rift basin (NFM) and forms an east-dipping low-angle fault. In contrast, the central parts of the ISTL fault segments are estimated to lie along the eastern boundary of the Matsumoto basin forming an oblique strike slip fault (Fig. 1)

Afterslip of the 14. August 2001 Earthquake (MW 6.4) Occurring Near the Northern Asperity of the 1968 Tokachi-oki Earthquake off the Pacific Coast of Northern Honshu, Japan

We investigated the rupture process of 2001 August 14 earthquake (MJ 6.2) that occurred at the eastern tip of a seismic gap off the Pacific coast of Aomori, northern Honshu, Japan. An average slip of 11cm on a fault size of 25×35km^2(MW=6.4) was estimated as the coseismic slip by inverting waveform data recorded by the K-Net. A detailed analysis of daily site positions of GPS stations from GEONET allowed us to find post-seismic horizontal displacements of several millimeters with a decaying-time constant of 2.2 months. The post-seismic deformation was explained by an afterslip that took place mainly on the northern periphery of the northern asperity of the 1968 Tokachi-oki earthquake (Mw 8.2). The seismic moment of the afterslip is estimated to be about three times greater (MW 6.7) than that of the coseismic slip. We infer that the afterslip has increased the earthquakegenerating stress in the northern asperity that has been considered a seismic gap since the occurrence of the 1994 Sanriku-haruka-oki earthquake (Mw 7.6). This slow event was not accompanied by any salient seismic activity

Cryo-EM structure of a Ca2⁺-bound photosynthetic LH1-RC complex containing multiple αβ-polypeptides

The light-harvesting-reaction center complex (LH1-RC) from the purple phototrophic bacterium Thiorhodovibrio strain 970 exhibits an LH1 absorption maximum at 960nm, the most red-shifted absorption for any bacteriochlorophyll (BChl) a-containing species. Here we present a cryo-EM structure of the strain 970 LH1-RC complex at 2.82 angstrom resolution. The LH1 forms a closed ring structure composed of sixteen pairs of the αβ-polypeptides. Sixteen Ca ions are present in the LH1 C-terminal domain and are coordinated by residues from the αβ -polypeptides that are hydrogen-bonded to BChl a. The Ca2⁺-facilitated hydrogen-bonding network forms the structural basis of the unusual LH1 redshift. The structure also revealed the arrangement of multiple forms of α- and β -polypeptides in an individual LH1 ring. Such organization indicates a mechanism of interplay between the expression and assembly of the LH1 complex that is regulated through interactions with the RC subunits inside

Earthquake source parameters determined by the SAFOD Pilot Hole seismic array

We estimate the source parameters of #3 microearthquakes by jointly analyzing seismograms recorded by the 32-level, 3-component seismic array installed in the SAFOD Pilot Hole. We applied an inversion procedure to estimate spectral parameters for the omega-square model (spectral level and corner frequency) and Q to displacement amplitude spectra. Because we expect spectral parameters and Q to vary slowly with depth in the well, we impose a smoothness constraint on those parameters as a function of depth using a linear first-difference operator. This method correctly resolves corner frequency and Q, which leads to a more accurate estimation of source parameters than can be obtained from single sensors. The stress drop of one example of the SAFOD target repeating earthquake falls in the range of typical tectonic earthquakes

Normal-faulting stress state associated with low differential stress in an overriding plate in northeast Japan prior to the 2011 Mw 9.0 Tohoku earthquake

Abstract Spatial and temporal variations in inland crustal stress prior to the 2011 Mw 9.0 Tohoku earthquake are investigated using focal mechanism solutions for shallow seismicity in Iwaki City, Japan. The multiple inverse method of stress tensor inversion detected two normal-faulting stress states that dominate in different regions. The stress field around Iwaki City changed from a NNW–SSE-trending triaxial extensional stress (stress regime A) to a NW–SE-trending axial tension (stress regime B) between 2005 and 2008. These stress changes may be the result of accumulated extensional stress associated with co- and post-seismic deformation due to the M7 class earthquakes. In this study we suggest that the stress state around Iwaki City prior to the 2011 Tohoku earthquake may have been extensional with a low differential stress. High pore pressure is required to cause earthquakes under such small differential stresses

Dynamic rupture propagation on geometrically complex fault with along-strike variation of fault maturity: insights from the 2014 Northern Nagano earthquake

Abstract Understanding the effect of the complex fault geometry on the dynamic rupture process and discriminating it from the complexity originating from the rheological properties of faults, is an essential subject in earthquake science. The 2014 Northern Nagano earthquake, which occurred near the end zone of a major active fault system, provided unique observations that enabled us to investigate both the detailed geometrical fault structure and surface deformation patterns as well as the temporal sequence led up from a prominent foreshock activity. We first develop a geometrical fault model with a substantial variation along strike, and a model for the regional stress field, which is well constrained by the observations. This significant along-strike variation in fault geometry probably reflects the difference of fault maturity at the end zone of the complex fault system. We used this model in order to conduct a set of dynamic rupture simulations using the highly efficient spatiotemporal boundary integral equation method. Based on our simulations, we show that the observed surface deformation can be reasonably explained as the effect of the non-planar fault geometry with a number of branch faults and bends. Graphical abstract

MOESM1 of Normal-faulting stress state associated with low differential stress in an overriding plate in northeast Japan prior to the 2011 Mw 9.0 Tohoku earthquake

Additional file 1. Fault slip data set obtained from focal mechanisms of earthquakes determined by Imanishi et al. (2012) around Iwaki City prior to the 2011 Tohoku earthquake

Engineering Evaluation of Tactile Warmth for Wood

Wood is a prospective resource from viewpoint of sustainable development. The engineering evaluation of tactile warmth is treated as a good point of wood. The relationship of the contact surface temperature and the thermal effusivity is derived from the theoretical analysis of heat transfer phenomenon and proposed as measures to evaluate the tactile warmth. The measures review some knowledge on tactile warmth of wood. It is found that the sensory warmth of wood has a high and positive linear correlation with the logarithm of the contact surface temperature and that the material with a lower thermal effusivity feels warmer than the material with a higher one. The relationship explains rationally why each wood has large difference of sensory warmth in spite of their small difference of material properties. The relationship also explains the reason why wood has good tactile warmth regardless of the season, which is different from metals