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Journal of Geophysical Research. Solid Earth

Kees Wapenaar, Myrna Staring
In seismic monitoring, one is usually interested in the response of a changing target zone, embedded in a static inhomogeneous medium. We introduce an efficient method that predicts reflection responses at the Earth's surface for different target-zone scenarios, from a single reflection response at the surface and a model of the changing target zone. The proposed process consists of two main steps. In the first step, the response of the original target zone is removed from the reflection response, using the Marchenko method...
June 2018: Journal of Geophysical Research. Solid Earth
Laura Parisi, Ana M G Ferreira, Jeroen Ritsema
Observations of shear wave anisotropy are key for understanding the mineralogical structure and flow in the mantle. Several researchers have reported the presence of seismic anisotropy in the lowermost 150-250 km of the mantle (i.e., D <mml:math xmlns:mml=""> <mml:msup> <mml:mrow/> <mml:mrow> <mml:mi>''</mml:mi> </mml:mrow> </mml:msup> </mml:math> layer), based on differences in the arrival times of vertically ( S V ) and horizontally ( S H ) polarized shear waves...
May 2018: Journal of Geophysical Research. Solid Earth
Andreas Fichtner, Saule Simutė
We present a probabilistic seismic point source inversion, taking into account 3-D heterogeneous Earth structure. Our method rests on (1) reciprocity and numerical wavefield simulations in complex media and (2) Hamiltonian Monte Carlo sampling that requires only a small amount of test models to provide reliable uncertainty information on the timing, location, and mechanism of the source. Using spectral element simulations of 3-D, viscoelastic, anisotropic wave propagation, we precompute receiver side strain tensors in time and space...
April 2018: Journal of Geophysical Research. Solid Earth
Caroline M Eakin, Catherine A Rychert, Nicholas Harmon
Mantle anisotropy beneath mid-ocean ridges and oceanic transforms is key to our understanding of seafloor spreading and underlying dynamics of divergent plate boundaries. Observations are sparse, however, given the remoteness of the oceans and the difficulties of seismic instrumentation. To overcome this, we utilize the global distribution of seismicity along transform faults to measure shear wave splitting of over 550 direct S phases recorded at 56 carefully selected seismic stations worldwide. Applying this source-side splitting technique allows for characterization of the upper mantle seismic anisotropy, and therefore the pattern of mantle flow, directly beneath seismically active transform faults...
February 2018: Journal of Geophysical Research. Solid Earth
M P A van den Ende, G Marketos, A R Niemeijer, C J Spiers
Intergranular pressure solution creep is an important deformation mechanism in the Earth's crust. The phenomenon has been frequently studied and several analytical models have been proposed that describe its constitutive behavior. These models require assumptions regarding the geometry of the aggregate and the grain size distribution in order to solve for the contact stresses and often neglect shear tractions. Furthermore, analytical models tend to overestimate experimental compaction rates at low porosities, an observation for which the underlying mechanisms remain to be elucidated...
January 2018: Journal of Geophysical Research. Solid Earth
M Queißer, M R Burton, F Arzilli, A Chiarugi, G I Marliyani, F Anggara, A Harijoko
Studying the quantity and origin of CO2 emitted by back-arc mud volcanoes is critical to correctly model fluid-dynamical, thermodynamical, and geochemical processes that drive their activity and to constrain their role in the global geochemical carbon cycle. We measured CO2 fluxes of the Bledug Kuwu mud volcano on the Kendeng Fold and thrust belt in the back arc of Central Java, Indonesia, using scanning remote sensing absorption spectroscopy. The data show that the expelled gas is rich in CO2 with a volume fraction of at least 16 vol %...
June 2017: Journal of Geophysical Research. Solid Earth
Fabian B Wadsworth, Jérémie Vasseur, Edward W Llewellin, Kimberly Genareau, Corrado Cimarelli, Donald B Dingwell
Volcanic ash particles can be remelted by the high temperatures induced in volcanic lightning discharges. The molten particles can round under surface tension then quench to produce glass spheres. Melting and rounding timescales for volcanic materials are strongly dependent on heating duration and peak temperature and are shorter for small particles than for large particles. Therefore, the size distribution of glass spheres recovered from ash deposits potentially record the short duration, high-temperature conditions of volcanic lightning discharges, which are hard to measure directly...
March 2017: Journal of Geophysical Research. Solid Earth
Quentin Simon, Nicolas Thouveny, Didier L Bourlès, Jean-Pierre Valet, Franck Bassinot, Lucie Ménabréaz, Valéry Guillou, Sandrine Choy, Luc Beaufort
Geomagnetic dipole moment variations associated with polarity reversals and excursions are expressed by large changes of the cosmogenic nuclide beryllium-10 ((10)Be) production rates. Authigenic (10)Be/(9)Be ratios (proxy of atmospheric (10)Be production) from oceanic cores therefore complete the classical information derived from relative paleointensity (RPI) records. This study presents new authigenic (10)Be/(9)Be ratio results obtained from cores MD05-2920 and MD05-2930 collected in the west equatorial Pacific Ocean...
November 2016: Journal of Geophysical Research. Solid Earth
William C Hammond, Geoffrey Blewitt, Corné Kreemer
We introduce Global Positioning System (GPS) Imaging, a new technique for robust estimation of the vertical velocity field of the Earth's surface, and apply it to the Sierra Nevada Mountain range in the western United States. Starting with vertical position time series from Global Positioning System (GPS) stations, we first estimate vertical velocities using the MIDAS robust trend estimator, which is insensitive to undocumented steps, outliers, seasonality, and heteroscedasticity. Using the Delaunay triangulation of station locations, we then apply a weighted median spatial filter to remove velocity outliers and enhance signals common to multiple stations...
October 2016: Journal of Geophysical Research. Solid Earth
Alba Martín-Español, Matt A King, Andrew Zammit-Mangion, Stuart B Andrews, Philip Moore, Jonathan L Bamber
In this work we assess the most recent estimates of glacial isostatic adjustment (GIA) for Antarctica, including those from both forward and inverse methods. The assessment is based on a comparison of the estimated uplift rates with a set of elastic-corrected GPS vertical velocities. These have been observed from an extensive GPS network and computed using data over the period 2009-2014. We find systematic underestimations of the observed uplift rates in both inverse and forward methods over specific regions of Antarctica characterized by low mantle viscosities and thin lithosphere, such as the northern Antarctic Peninsula and the Amundsen Sea Embayment, where its recent ice discharge history is likely to be playing a role in current GIA...
September 2016: Journal of Geophysical Research. Solid Earth
Hélène Le Mével, Patricia M Gregg, Kurt L Feigl
Moving beyond the widely used kinematic models for the deformation sources, we present a new dynamic model to describe the process of injecting magma into an existing magma reservoir. To validate this model, we derive an analytical solution and compare its results to those calculated using the Finite Element Method. A Newtonian fluid characterized by its viscosity, density, and overpressure (relative to the lithostatic value) flows through a vertical conduit, intruding into a reservoir embedded in an elastic domain, leading to an increase in reservoir pressure and time-dependent surface deformation...
August 2016: Journal of Geophysical Research. Solid Earth
J Maarten de Moor, A Aiuppa, G Avard, H Wehrmann, N Dunbar, C Muller, G Tamburello, G Giudice, M Liuzzo, R Moretti, V Conde, B Galle
Eruptive activity at Turrialba Volcano (Costa Rica) has escalated significantly since 2014, causing airport and school closures in the capital city of San José. Whether or not new magma is involved in the current unrest seems probable but remains a matter of debate as ash deposits are dominated by hydrothermal material. Here we use high-frequency gas monitoring to track the behavior of the volcano between 2014 and 2015 and to decipher magmatic versus hydrothermal contributions to the eruptions. Pulses of deeply derived CO2-rich gas (CO2/Stotal > 4...
August 2016: Journal of Geophysical Research. Solid Earth
Geoffrey Blewitt, Corné Kreemer, William C Hammond, Julien Gazeaux
Automatic estimation of velocities from GPS coordinate time series is becoming required to cope with the exponentially increasing flood of available data, but problems detectable to the human eye are often overlooked. This motivates us to find an automatic and accurate estimator of trend that is resistant to common problems such as step discontinuities, outliers, seasonality, skewness, and heteroscedasticity. Developed here, Median Interannual Difference Adjusted for Skewness (MIDAS) is a variant of the Theil-Sen median trend estimator, for which the ordinary version is the median of slopes vij  = (xj-xi )/(tj-ti ) computed between all data pairs i > j...
March 2016: Journal of Geophysical Research. Solid Earth
A R Niemeijer, C Boulton, V G Toy, J Townend, R Sutherland
The Alpine Fault, New Zealand, is a major plate-bounding fault that accommodates 65-75% of the total relative motion between the Australian and Pacific plates. Here we present data on the hydrothermal frictional properties of Alpine Fault rocks that surround the principal slip zones (PSZ) of the Alpine Fault and those comprising the PSZ itself. The samples were retrieved from relatively shallow depths during phase 1 of the Deep Fault Drilling Project (DFDP-1) at Gaunt Creek. Simulated fault gouges were sheared at temperatures of 25, 150, 300, 450, and 600°C in order to determine the friction coefficient as well as the velocity dependence of friction...
February 2016: Journal of Geophysical Research. Solid Earth
Wei Tao, Timothy Masterlark, Zheng-Kang Shen, Erika Ronchin
Impoundment of the Zipingpu reservoir (ZR), China, began in September 2005 and was followed 2.7 years later by the 2008 Mw 7.9 Wenchuan earthquake (WE) rupturing the Longmen Shan Fault (LSF), with its epicenter ~12 km away from the ZR. Based on the poroelastic theory, we employ three-dimensional finite element models to simulate the evolution of stress and pore pressure due to reservoir impoundment, and its effect on the Coulomb failure stress on the LSF. The results indicate that the reservoir impoundment formed a pore pressure front that slowly propagated through the crust with fluid diffusion...
October 2015: Journal of Geophysical Research. Solid Earth
I Bianchi, G Bokelmann, K Shiomi
Northern Japan is a tectonically active area, with the presence of several volcanoes, and with frequent earthquakes among which the destructive M w  = 8.9-9.0 Tohoku-oki occurred on 11 March 2011. Tectonic activity leaves an imprint on the crustal structures, on both the upper and the lower layers. To investigate the crust in northern Japan, we construct a receiver function data set using teleseismic events recorded at 58 seismic stations belonging to the Japanese National (Hi-net) network. We isolate the signals, in the receiver function wavelet, that witness the presence of anisotropic structures at depth, with the aim of mapping the variation of anisotropy across the northern part of the island...
July 2015: Journal of Geophysical Research. Solid Earth
Ki-Weon Seo, Clark R Wilson, Ted Scambos, Baek-Min Kim, Duane E Waliser, Baijun Tian, Byeong-Hoon Kim, Jooyoung Eom
Recent observations from satellite gravimetry (the Gravity Recovery and Climate Experiment (GRACE) mission) suggest an acceleration of ice mass loss from the Antarctic Ice Sheet (AIS). The contribution of surface mass balance changes (due to variable precipitation) is compared with GRACE-derived mass loss acceleration by assessing the estimated contribution of snow mass from meteorological reanalysis data. We find that over much of the continent, the acceleration can be explained by precipitation anomalies...
May 2015: Journal of Geophysical Research. Solid Earth
B P Proctor, T M Mitchell, G Hirth, D Goldsby, F Zorzi, J D Platt, G Di Toro
To investigate differences in the frictional behavior between initially bare rock surfaces of serpentinite and powdered serpentinite ("gouge") at subseismic to seismic slip rates, we conducted single-velocity step and multiple-velocity step friction experiments on an antigorite-rich and lizardite-rich serpentinite at slip rates (V) from 0.003 m/s to 6.5 m/s, sliding displacements up to 1.6 m, and normal stresses (σn ) up to 22 MPa for gouge and 97 MPa for bare surfaces. Nominal steady state friction values (μ nss) in gouge at V = 1 m/s are larger than in bare surfaces for all σn tested and demonstrate a strong σn dependence; μ nss decreased from 0...
November 2014: Journal of Geophysical Research. Solid Earth
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