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Effect of pressure on temperature measurements using WRe thermocouple and its geophysical impact
Publication date: Available online 12 November 2019Source: Physics of the Earth and Planetary InteriorsAuthor(s): Yu Nishihara, Shunta Doi, Sho Kakizawa, Yuji Higo, Yoshinori TangeAbstractOur understanding of the Earth's interior strongly depends on the physical and chemical properties of the Earth's constituent materials, which have been determined using high-pressure/high-temperature experiments involving thermocouples. Thus, knowledge of the pressure effect on the thermocouple electromotive force (EMF) is indispensable for an accurate understanding of the Earth's interior. We have determined the effect of pressure on a ...
Source: Physics of the Earth and Planetary Interiors - November 13, 2019 Category: Physics Source Type: research

Structural heterogeneity and megathrust earthquakes in Southwest Japan
In this study, we present 3-D high-resolution P and S wave velocity and Poisson's ratio images of the Nankai subduction zone, which are determined using a large number of high-quality arrival-time data of well-located onshore and offshore local earthquakes. The obtained seismic images, as well as residual topography and gravity anomalies, show similar structures in both the upper and lower plates above and below the rupture zones of the 1944 Tonankai earthquake (M 8.1), the 1946 Nankai earthquake (M 8.3), and the 1968 Hyuganada earthquake (M 7.5). These results indicate that the nucleation and rupture processes of these me...
Source: Physics of the Earth and Planetary Interiors - November 12, 2019 Category: Physics Source Type: research

How far does a subduction wedge follow lubrication dynamics?
This article aims to address a fundamental question - is the lubrication theory valid for subduction wedges with α ≫ 1°? We test the validity by comparing its analytical solutions with the results obtained from the numerical solutions of full-form Stokes equations, and constrain α limit (<20°) in applying the lubrication theory with errors <5%. We also use this theory to evaluate the magnitude of dynamic pressure in subduction wedges as a function of subduction velocity, wedge geometry and its viscosity, and then demonstrate how such dynamic pressure eventually controls the overriding plate deformation an...
Source: Physics of the Earth and Planetary Interiors - November 9, 2019 Category: Physics Source Type: research

Investigating the strength and trend of seismic anisotropy in the western part of Makran subduction zone and southeast of Iran
Publication date: Available online 6 November 2019Source: Physics of the Earth and Planetary InteriorsAuthor(s): Saeid Rahimzadeh, Ali Moradi, Ayoub KavianiAbstractThe Makran subduction zone, located in southeastern Iran and southern Pakistan, extends approximately 900 km along the Eurasian-Arabian plate boundary, where the Arabian oceanic plate subducts beneath the Eurasian plate. Using broadband seismic data recorded in the western part of Makran in the southeast of Iran, seismic anisotropy was studied to better understand geodynamic processes of this subduction zone. We analyzed shear wave splitting of core-refracted ...
Source: Physics of the Earth and Planetary Interiors - November 7, 2019 Category: Physics Source Type: research

Simultaneous tomography of all periods in surface wave analysis
Publication date: Available online 7 November 2019Source: Physics of the Earth and Planetary InteriorsAuthor(s): Najmieh Mohammadi, Ali Gholami, Habib Rahimi, Abdelkrim AoudiaAbstractTwo dimensional surface wave travel time tomography is one of the most practical methods to image the lateral variation of phase/group velocity. In practice, local dispersion curves are reconstructed by performing 2-D inversion of travel times for a series of periods separately. Although 2-D inversion is numerically efficient, it does not consider the dependency between periods and thus can lead to a suboptimal phase/group velocity. To address...
Source: Physics of the Earth and Planetary Interiors - November 7, 2019 Category: Physics Source Type: research

Editorial Board
Publication date: November 2019Source: Physics of the Earth and Planetary Interiors, Volume 296Author(s): (Source: Physics of the Earth and Planetary Interiors)
Source: Physics of the Earth and Planetary Interiors - November 6, 2019 Category: Physics Source Type: research

New insights into seismic absorption imaging
Publication date: Available online 1 November 2019Source: Physics of the Earth and Planetary InteriorsAuthor(s): Panayiota Sketsiou, Ferdinando Napolitano, Aristides Zenonos, Luca De SienaAbstractIn recent years, attenuation has been used as a marker for source and dynamic Earth processes due to its higher sensitivity to small variations of lithospheric properties compared to seismic velocity. From seismic hazard analysis to oil and gas exploration and rock physics, many fields need a better reconstruction of energy absorption, a constituent of seismic attenuation generally considered a reliable marker of fluid saturation ...
Source: Physics of the Earth and Planetary Interiors - November 3, 2019 Category: Physics Source Type: research

Moment rate of the 2018 Gulf of Alaska earthquake
Publication date: Available online 1 November 2019Source: Physics of the Earth and Planetary InteriorsAuthor(s): Stefano Santini, Michele DragoniAbstractThe 2018 Gulf of Alaska earthquake (Mw 7.9) occurred in a region of the Pacific plate southwest of the Alaskan subduction zone. The earthquake was a strike-slip event, with the hypocenter located at a depth of about 25 km and a seismic moment equal to 0.96 × 1021 Nm. Two observed moment rates have been obtained by the Geoscope Observatory, France, and by the United States Geological Survey (USGS). Both of them can be interpreted as due to the failure of two asperities...
Source: Physics of the Earth and Planetary Interiors - November 1, 2019 Category: Physics Source Type: research

Importance of later phases in seismic tomography
Publication date: November 2019Source: Physics of the Earth and Planetary Interiors, Volume 296Author(s): Dapeng ZhaoAbstractSeismic tomography is a powerful tool for mapping the three-dimensional structure of the Earth's interior. Tomographic images obtained in the past four decades have greatly improved our understanding of the Earth's heterogeneous structure and dynamics, which signify a revolution in Earth sciences. Most of the tomographic models are determined using the first P and S wave data generated by local earthquakes and/or teleseismic events. Five global seismic discontinuities exist in the Earth, including th...
Source: Physics of the Earth and Planetary Interiors - November 1, 2019 Category: Physics Source Type: research

Disparate behaviour of deformation patterns beneath northeast Indian lithosphere inferred from shear wave splitting analysis
Publication date: Available online 30 October 2019Source: Physics of the Earth and Planetary InteriorsAuthor(s): Debasis D. Mohanty, Poulommi MondalAbstractNew shear wave splitting measurements are obtained from the North East Indian region utilizing the core refracted PKS/SKS/SKKS phases, suggesting the region as more complex and anisotropic in nature. The splitting parameters namely time delays (δt) and fast polarization directions (ϕ) are computed at nine stations and the results are found to be more consistent with the geologic/tectonic structures and present mantle deformation patterns under this particular region. ...
Source: Physics of the Earth and Planetary Interiors - October 31, 2019 Category: Physics Source Type: research

Effects of Coulomb stress change on Mw > 6 earthquakes in the Caucasus region
Publication date: December 2019Source: Physics of the Earth and Planetary Interiors, Volume 297Author(s): Bahruz Ahadov, Shuanggen JinAbstractCoulomb stress variations may trigger earthquakes, while the stress transfer process is not clear. In this paper, Coulomb stress changes are investigated for the sequences of strong earthquakes in the Caucasus region, which followed the 1988 Mw6.8 in Spitak, the 1991 Mw6.9 in Racha and the 2000 Mw6.2 in Baku. Our results show that the mainshocks induced variations in the stress field where most of the seismic events occurred. Coulomb stress increases 2 bars corresponding nearly to ...
Source: Physics of the Earth and Planetary Interiors - October 31, 2019 Category: Physics Source Type: research

Two-stage modeling of Strombolian-type eruptions and quantification of the model parameters: Insight from the seismic and acoustic signals
Publication date: December 2019Source: Physics of the Earth and Planetary Interiors, Volume 297Author(s): Vyacheslav M. Zobin, Jean Battaglia, William Melson, Yasuaki SudoAbstractThe seismic signals of majority Strombolian explosions show a two-phase structure that may be the result of a two-stage explosive eruption. We quantify the parameters of two proposed stages of Strombolian eruptions at volcanoes Arenal, Aso and Yasur using 193 seismic records and 18 acoustic signals and considering that the first stage of eruption represents the seismically active process of the gas slug expansion and ascent (GSEA) in the conduit a...
Source: Physics of the Earth and Planetary Interiors - October 29, 2019 Category: Physics Source Type: research

Attenuation of high frequency body waves in the crust of western Tibet
Publication date: Available online 28 October 2019Source: Physics of the Earth and Planetary InteriorsAuthor(s): Rahul Biswas, Chandrani SinghAbstractThe attenuation characteristics of western Tibet have been analyzed by estimating the seismic attenuation parameters (Qp−1 and Qs−1) at five different central frequencies (1.5, 3, 6, 12 and 18 Hz). The extended coda normalization method has been used on 469 three component local earthquakes which are recorded at Y2 network of broadband stations deployed in western Tibet during 2007-2011 years. We have estimated the frequency dependent Qp−1 and Qs−1 values at each stat...
Source: Physics of the Earth and Planetary Interiors - October 28, 2019 Category: Physics Source Type: research

Crustal structure and lateral variations in Moho beneath the Delhi fold belt, NW India: Insight from gravity data modeling and inversion
Publication date: December 2019Source: Physics of the Earth and Planetary Interiors, Volume 297Author(s): Divyanshu Dwivedi, Ashutosh Chamoli, Anand K. PandeyAbstractThe Proterozoic Delhi fold belt (DFB) in NW India shows a prominent NNE-SSW trending gravity high, but its northward extension beneath Gangetic alluvium lack understanding. We model the gravity anomaly using radially averaged power spectrum, depth from extreme points (DEXP) method, wavelength filtering, 3D structural inversion to constrain crustal structure of the DFB. The radially averaged power spectrum analysis suggests three interfaces and the DEXP method ...
Source: Physics of the Earth and Planetary Interiors - October 26, 2019 Category: Physics Source Type: research

Extremely young melt infiltration of the sub-continental lithospheric mantle
Publication date: Available online 23 October 2019Source: Physics of the Earth and Planetary InteriorsAuthor(s): Simon Turner, Michael Turner, Bernard Bourdon, Kari Cooper, Don PorcelliAbstractIt has long been inferred that mantle metasomatism and the incompatible element enrichment of the continents both require movement of melts formed by very low degree melting of the mantle. Yet establishing the presence of these melts and whether this process is on-going and continuous, or spatially and temporally restricted, has proved difficult. Here we report large U-Th-Ra disequilibria in metasomatised, mantle xenoliths erupted in...
Source: Physics of the Earth and Planetary Interiors - October 25, 2019 Category: Physics Source Type: research