Seismic harmonic tremors and interpretation of their origins in relation to cryosphere dynamics in April 2015 around the Lutzow-Holm Bay, East Antarctica

The Tenth Symposium on Polar Science/Ordinary sessions: [OG] Polar Geosciences, Wed. 4 Dec. / 3F Seminar room, National Institute of Polar Researc

Episodic transient deformation revealed by the analysis of multiple GNSS networks in the Noto Peninsula, central Japan

流体とスロースリップに駆動された能登半島群発地震 --ソフトバンク独自基準点データを用いた地殻変動解析結果--. 京都大学プレスリリース. 2023-06-13.Since November 30, 2020, an intense seismic swarm and transient deformation have been continuously observed in the Noto Peninsula, central Japan, which is a non-volcanic/geothermal area far from major plate boundaries. We modeled transient deformation based on a combined analysis of multiple Global Navigation Satellite System (GNSS) observation networks, including one operated by a private sector company (SoftBank Corp.), relocated earthquake hypocenters, and tectonic settings. Our analysis showed a total displacement pattern over 2 years shows horizontal inflation and uplift of up to ~ 70 mm around the source of the earthquake swarm. In the first 3 months, the opening of the shallow-dipping tensile crack had an estimated volumetric increase of ~ 1.4 × 10⁷ m³ at a depth of ~ 16 km. Over the next 15 months, the observed deformation was well reproduced by shear-tensile sources, which represent an aseismic reverse-type slip and the opening of a southeast-dipping fault zone at a depth of 14–16 km. We suggest that the upwelling fluid spread at a depth of ~ 16 km through an existing shallow-dipping permeable fault zone and then diffused into the fault zone, triggering a long-lasting sub-meter aseismic slip below the seismogenic depth. The aseismic slip further triggered intense earthquake swarms at the updip

Josephson junction in cobalt-doped BaFe2As2 epitaxial thin films on (La, Sr)(Al, Ta)O3 bicrystal substrates

Josephson junctions were fabricated in epitaxial films of cobalt-doped BaFe2As2 on [001]-tilt (La,Sr)(Al,Ta)O3 bicrystal substrates. 10m-wide microbridges spanning a 30-degrees-tilted bicrystal grain boundary (BGB bridge) exhibited resistively-shunted-junction (RSJ)-like current-voltage characteristics up to 17 K, and the critical current was suppressed remarkably by a magnetic field. Microbridges without a BGB did not show the RSJ-like behavior, and their critical current densities were 20 times larger than those of BGB bridges, confirming BGB bridges display a Josephson effect originating from weakly-linked BGB

Scaling relationships between sizes of nucleation regions and eventual sizes of microearthquakes

金沢大学大学院自然科学研究科自然計測We investigate the initial rupture process of microearthquakes to reveal relationships between nucleation region sizes and eventual earthquake sizes. In order to obtain high quality waveform data, we installed a trigger recording system with a sampling frequency of 10 kHz at the base of a deep borehole at the Nojima Fault, Japan. We analyze waveform data of 31 events around the borehole, with seismic moment ranging from 4.2 × 109 Nm to 7.1 × 1011 Nm. We use both a circular crack model with an accelerating rupture velocity (SK model) [Sato, T., Kanamori, H., 1999. Beginning of earthquakes modeled with the Griffith\u27s fracture criterion, Bull. Seism. Soc. Am., 89, 80-93.], which generates a slow initial phase of velocity pulse, and a circular crack model with a constant rupture velocity (SH model) [Sato, T, Hirasawa, T., 1973. Body wave spectra from propagating shear cracks, J. Phys. Earth, 21, 415-431.], which generates a ramp-like velocity pulse. Source parameters of these two models are estimated by waveform inversion of the first half cycle of the observed velocity pulse applying both a grid search and a non-linear least squares method. 14 of 31 events are never reproduced by the SH model with a constant Q operator. But SK model with a constant Q operator provides a size of the pre-existing crack, corresponding to the size of the nucleation regions, and a size of the eventual crack. We recognize that (i) the eventual seismic moment is approximately scaled as the cube of the size of pre-existing cracks, (ii) the eventual seismic moment is scaled as the cube of the size of eventual cracks, and (iii) the size of eventual cracks is roughly proportional to the size of pre-existing cracks. We, thus, conclude that the size of eventual earthquakes is controlled by the size of the nucleation regions. © 2007 Elsevier B.V. All rights reserved

Landslide displacement detection around Hakusan volcano, central Japan, from InSAR analysis of ALOS-2/PALSAR-2 data

nSAR analysis using ALOS-2/PALSAR-2 data was conducted to detect landslides around Hakusan volcano, where we observed landslide movements in three areas. In the Jinnosukedani area, we detected landslide movement with maximum annual displacement of 200 mm, which is consistent with that of GNSS observations on the ground surface. In the Yunotani area, we detected landslide movement with maximum annual displacement of 200 mm. The landslide area detected by the InSAR analysis is almost coincident with a previous study of InSAR analysis, although the remarkable landslide area with annual displacement of 100–200 mm is narrower than that reported by the previous study. In the Sennindani area, a large slope collapse can be captured by InSAR analysis as a low coherence area. InSAR analysis around Hakusan volcano provides results that are consistent with those of the ground-based monitoring in the field, indicating that InSAR analysis is a useful landslide-monitoring tool

Spatial variation in coda Q around the Nobi fault zone, central Japan: Relation to S-wave velocity and seismicity

We investigate the spatial variation in coda Q around the Nobi fault zone in a high strain rate zone to assess the relation between coda Q, shear wave velocity, and seismicity. Waveform data were obtained from dense seismic observations. Low coda Q that follows the Niigata-Kobe Tectonic Zone in the high strain rate zone is distinct at the lowest frequency band of 1 to 2∈Hz. However, at higher frequencies, such a spatial pattern in coda Q is unclear. A good positive correlation was found between coda Q at the 1- to 2-Hz frequency band and the S-wave velocity perturbation at 25-km depth, which suggests that the coda Q reflects the ductile deformation below the brittle-ductile transition zone. Furthermore, coda Q at the 1- to 2-Hz frequency band correlates negatively with seismicity at 10- to 15-km depth, which implies that there is a high stressing rate in the low coda Q area. These facts, together with results of previous studies, imply that a high deformation rate below the brittle-ductile transition zone produces the high strain rate observed by the Global Positioning System (GPS) on the surface in this region

Biaxially textured cobalt-doped BaFe2As2 films with high critical current density over 1 MA/cm2 on MgO-buffered metal-tape flexible substrates

High critical current densities (Jc) > 1 MA/cm2 were realized in cobalt-doped BaFe2As2 (BaFe2As2:Co) films on flexible metal substrates with biaxially-textured MgO base-layers fabricated by an ion-beam assisted deposition technique. The BaFe2As2:Co films showed small in-plane crystalline misorientations (delta fai BaFe2As2:Co) of ~3o regardless of doubly larger misorientaions of the MgO base-layers (delta fai MgO = 7.3o), and exhibited high self-field Jc up to 3.5 MA/cm2 at 2 K. These values are comparable to that on MgO single crystals and the highest Jc among iron pnictide superconducting tapes and wires ever reported. High in-field Jc suggests the existence of c-axis correlated vortex pinning centers.Comment: Published in Appl. Phys. Let

Relationship of the number and size of superficial groin lymph nodes with the stage of secondary lymphatic edema

PURPOSE: This study evaluated the relationships of the size and number of superficial groin lymph nodes with the lower limb lymphedema stage and thus examined the role of superficial lymphatic lymph nodes in secondary lymphedema development. METHODS: We determined the number and size of superficial groin lymph nodes using horizontal plane computed tomography (CT) and the lymphedema stage in the lower limbs of 25 patients with gynecologic cancer. RESULTS: The patients had an average of 2.92 (range, 1-7) superficial groin lymph nodes; the mean size of the 146 evaluated lymph nodes was 7.55 mm (range, 5-15 mm). In 19 of 25 patients (76%), the side with major edema contained fewer superficial groin lymph nodes. In total, 22 patients (88%) had fewer superficial groin lymph nodes or a smaller total lymph node size on the edematous dominant side. CONCLUSIONS: In this evaluation of the link between superficial groin lymph node laterality and secondary lymphedema staging, we found that patients with large lymph node numbers and sizes tended to present with a relatively earlier stage of lymphedema. Our results therefore suggest that the size and number of superficial groin lymph nodes affect the lymphedema stage

Deep low-frequency tremors as a proxy for slip monitoring at plate interface

金沢大学理工研究域自然システム学系We propose a new method to monitor slip at the plate interface using non-volcanic deep-low frequency (DLF) tremors. We assume that a DLF tremor is the superposition of frequently excited intermittent events, meaning that the envelope of the reduced displacement of the DLF tremor provides an apparent moment rate function. We estimate a conversion factor from the apparent moment to the seismic moment with an assumption that a total size of DLF tremors of an episode is proportional to the size of corresponding slow slip event (SSE). The cumulative seismic moment estimated by DLF tremors is consistent with that estimated from geodetic methods and provides appropriate slip and slip rate at the plate interface. This proves our assumptions and demonstrates that DLF tremors are useful tool for realtime monitoring of the slip at the plate interface. Copyright 2008 by the American Geophysical Union