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Kauri Tree‐Ring Stable Isotopes Reveal a Centennial Climate Downturn Following the Antarctic Cold Reversal in New Zealand Geophys. Res. Lett. (IF 4.497) Pub Date : 2020-12-22 M. Pauly; C. S. M. Turney; J. G. Palmer; U. Büntgen; A. Brauer; G. Helle
The dynamics of the Late Glacial have been demonstrated by numerous records from the Northern Hemisphere and far fewer from the Southern Hemisphere (SH). SH paleoclimate records reveal a general warming trend, interrupted by a deglaciation pause Antarctic Cold Reversal (ACR; ∼14,700–13,000 cal BP). Here, we present decadal tree‐ring stable isotope chronologies (δ18O, δ13C) from New Zealand (NZ) subfossil
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Comparisons of Satellite and Airborne Altimetry With Ground‐Based Data From the Interior of the Antarctic Ice Sheet Geophys. Res. Lett. (IF 4.497) Pub Date : 2020-12-11 K. M. Brunt; B. E. Smith; T. C. Sutterley; N. T. Kurtz; T. A. Neumann
A series of traverses has been conducted for validation of the National Aeronautics and Space Administration Ice, Cloud, and land Elevation Satellite 2 (ICESat‐2) on the flat interior of the Antarctic ice sheet. Global Navigation Satellite System data collected on three separate 88S Traverses intersect 20% of the ICESat‐2 reference ground tracks and have precisions of better than ±7 cm and biases of
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Particulate Backscattering in the Global Ocean: A Comparison of Independent Assessments Geophys. Res. Lett. (IF 4.497) Pub Date : 2020-12-14 K. M. Bisson; E. Boss; P. J. Werdell; A. Ibrahim; M. J. Behrenfeld
How well do we know the particulate backscattering coefficient (bbp) in the global ocean? Satellite lidar bbp has never been validated globally and few studies have compared lidar bbp to bbp derived from reflectances (via ocean color) or in situ observations. Here, we validate lidar bbp with autonomous biogeochemical Argo floats using a decorrelation analysis to identify relevant spatiotemporal matchup
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Subpolar Activation of Halogen Heterogeneous Chemistry in Austral Spring Geophys. Res. Lett. (IF 4.497) Pub Date : 2020-12-06 Brian Zambri; Douglas E. Kinnison; Susan Solomon
Heterogeneous halogen chemistry plays a dominant role in driving changes in polar chemical composition and ozone depletion. Activation of halogens outside the polar regions may result in depletion of local ozone, along with changes in the chemical budgets of various species in the lower stratosphere (LS). In this study, the means and distributions of NO2 measurements from the Stratospheric Aerosol
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A Simple Method for Predicting Intensity Change Using the Peak Time Lag Between Lightning and Wind in Tropical Cyclones Geophys. Res. Lett. (IF 4.497) Pub Date : 2020-12-22 Xiangzhen Kong; Yang Zhao; Zhenfeng Qiu; Xinyi Tao; Wenjuan Zhang
Using lightning data from the World‐Wide Lightning Location Network (WWLLN) and tracking data for Tropical Cyclones (TCs) from the China Meteorological Administration (CMA), the relationship between the peak time lag (Tlag) and the wind intensity change in severe and super typhoons was investigated. The Tlag between the maximum peaks of the inner‐core lightning and the TC intensity ranged from −132
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The Extreme Positive Indian Ocean Dipole of 2019 and Associated Indian Summer Monsoon Rainfall Response Geophys. Res. Lett. (IF 4.497) Pub Date : 2020-12-22 Satyaban B. Ratna; Annalisa Cherchi; Timothy J. Osborn; Manoj Joshi; Umakanth Uppara
The positive Indian Ocean Dipole (IOD) event in 2019 was among the strongest on record, while the Indian Summer monsoon (ISM) was anomalously dry in June then very wet by September. We investigated the relationships between the IOD, Pacific sea surface temperature (SST), and ISM rainfall during 2019 with an atmospheric general circulation model forced by observed SST anomalies. The results show that
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The Atmospheric Response to North Atlantic SST Trends, 1870–2019 Geophys. Res. Lett. (IF 4.497) Pub Date : 2020-12-22 Kristopher B. Karnauskas; Lei Zhang; Dillon J. Amaya
Sea surface temperature (SST) observations in the North Atlantic since 1870 reveal a region of enhanced warming off the northeastern coast of North America, and a region of cooling to the south of Greenland. It has been hypothesized that these adjacent SST trends are a result of long‐term changes in the buoyancy‐driven ocean circulation—a slowdown of the Atlantic Meridional Overturning Circulation
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Prompt Emergence and Disappearance of EMIC Waves Driven by the Sequentially Enhanced Solar Wind Dynamic Pressure Geophys. Res. Lett. (IF 4.497) Pub Date : 2020-12-28 Zuxiang Xue; Zhigang Yuan; Xiongdong Yu
Van Allen Probes (VAPs) and multiple ground‐based stations simultaneously observed prompt emergences and disappearances of electromagnetic ion cyclotron (EMIC) waves driven by the sequentially enhanced solar wind dynamic pressures in the dayside inner magnetosphere on November 6, 2015. The measured hot protons (>60 keV) display enhancements of perpendicular temperature during compressions, which provides
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The Effect of Aerosols on Fog Lifetime: Observational Evidence and Model Simulations Geophys. Res. Lett. (IF 4.497) Pub Date : 2020-12-28 Shuqi Yan; Bin Zhu; Tong Zhu; Chune Shi; Duanyang Liu; Hanqing Kang; Wen Lu; Chunsong Lu
The aerosol–cloud interaction (ACI) and aerosol–radiation interaction (ARI) have notable influences on clouds, but their effects on fog are rarely analyzed before. Previous studies indicate that fog frequency in East China has been decreasing, and we further reveal that fog duration increases during 1960–2010. We hypothesize that this trend is related to the increase of aerosol pollution and perform
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Is Mesospheric Quasi Biennial Oscillation Ephemeral? Geophys. Res. Lett. (IF 4.497) Pub Date : 2020-12-28 Karanam Kishore Kumar
The time evolution of mesospheric quasi biennial oscillation (MQBO) in the 82–98 km altitude region using long‐term meteor radar observations over low and equatorial latitudes and TIMED Doppler Interferometer (TIDI) observations is discussed for the first time. The wavelet spectra of monthly mean zonal winds over Serpog (6.4°S, 106.7°E; 1993–1998), Koto Tabang (0.2°S, 100.3°E; 2003–2012) and Thumba
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A Survey of Photoelectrons on the Nightside of Mars Geophys. Res. Lett. (IF 4.497) Pub Date : 2020-12-28 Y. ‐T. Cao; J. Cui; X. ‐S. Wu; D. ‐D. Niu; H. ‐R. Lai; B. ‐B. Ni; Q. Luo; J. Yu; Y. Wei
Despite produced exclusively on the dayside, photoelectrons, as an important population of the Martian ionosphere, have also been observed on the nightside. Here we present a statistical survey of nightside photoelectrons using the suprathermal electron measurements, made by the Solar Wind Electron Analyzer onboard the Mars Atmosphere and Volatile Evolution. We find that nearly 30% of the available
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Hourly Surface Observations Suggest Stronger Solar Dimming and Brightening at Sunrise and Sunset Over China Geophys. Res. Lett. (IF 4.497) Pub Date : 2020-12-28 Yawen Wang; Jiahua Zhang; Arturo Sanchez‐Lorenzo; Katsumasa Tanaka; Jörg Trentmann; Wenping Yuan; Martin Wild
Exploration of the diurnal pattern of global dimming and brightening has been limited by the paucity of high‐temporal resolution observations. Based on 22 years’ continuous observations of hourly surface solar radiation (SSR) over 96 stations across China for 1993–2014, this study evidences higher relative changes in diurnal SSR in terms of both frequency and magnitude at sunrise and sunset, with a
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Increasing Synchronous Fire Danger in Forests of the Western United States Geophys. Res. Lett. (IF 4.497) Pub Date : 2020-12-28 John T. Abatzoglou; Caroline S. Juang; A. Park Williams; Crystal A. Kolden; Anthony LeRoy Westerling
Widespread fire activity taxes suppression resources and can compound wildfire hazards. We examine the geographic synchronicity of fire danger across western United States forests as a proxy for the strain on fire suppression resource availability. Interannual variability in the number of days with synchronous fire danger, defined as fire weather indices exceeding the local 90th percentile across ≥40%
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Barrovian metamorphism of the metapelites in NE Sikkim (Eastern Himalaya): Constraints from chemographic projection and geothermobarometry J. Asian Earth Sci. (IF 3.059) Pub Date : 2021-01-14 Suparna Tewari; Divya Prakash; Manoj Kumar Yadav; Vedika Srivastava
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Theoretical Study and Application of Rate Transient Analysis on Complex Fractured-Caved Carbonate Reservoirs Geofluids (IF 1.534) Pub Date : 2021-01-25 Qingyan Yu; Qi Wang; Pengcheng Liu; Jing Zhang; Qi Zhang; Xiaojuan Deng; Kai Feng
Carbonate reservoirs are mainly fractured-caved reservoirs with very well-developed dissolved pores, fractures, and caves. They have strong heterogeneity with various types of reservoir pore spaces. Using seismic inversion and reservoir static characterization, the result shows that the fractured-caved carbonate rocks in China are mainly caves with poor connectivity and complex oil-water distribution
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Foliage Senescence as a Key Parameter for Modeling Gross Primary Productivity in a Mediterranean Shrubland J. Geophys. Res. Biogeosci. (IF 3.406) Pub Date : 2020-12-06 Alejandro Cueva; Stephen H. Bullock; Rodrigo Méndez‐Alonzo; Eulogio López‐Reyes; Rodrigo Vargas
Although drylands cover >40% of the land surface, models of ecosystem gross primary productivity (GPP) generally have been designed for mesic temperate ecosystems. Arguably, GPP models often lack a good representation of vegetation phenology, particularly not estimating the ecosystem effects of the prolonged foliage senescence which may be common in drylands. To estimate daily GPP for a water‐limited
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Evaluation of Three Numerical Weather Prediction Models for the Weddell Sea Region for the Austral Winter 2013 J. Geophys. Res. Atmos. (IF 3.821) Pub Date : 2020-12-19 M. O. Jonassen; T. Nygård; T. Vihma
It is widely recognized that numerical weather prediction (NWP) results for the Antarctic are relatively poor compared to the mid‐latitudes. In this study, we evaluate output from three operational NWP systems: the ECMWF, Global Forecast System (GFS) and Antarctic Mesoscale Prediction System (AMPS), for the Austral winter (June‐August) of 2013 for the Weddell Sea region, paying special attention to
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A Computationally Efficient Ensemble Filtering Scheme for Quantitative Volcanic Ash Forecasts J. Geophys. Res. Atmos. (IF 3.821) Pub Date : 2020-12-02 Meelis J. Zidikheri; Christopher Lucas
A method of assimilating satellite observations in quantitative ensemble forecasting models of airborne volcanic ash is presented in this study. The method employs many trial dispersion model simulations that are generated by both deterministic and random perturbations of the source term and use of an ensemble of numerical weather prediction model fields. An ensemble filter is then applied to the trial
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Future Changes in the Asian‐Australian Monsoon System With 1.5°C and 2°C Rise in Temperature J. Geophys. Res. Atmos. (IF 3.821) Pub Date : 2020-12-22 Hui Wang; Zhenming Ji; Xian Zhu; Lei Lin; Wenjie Dong
Future changes in the Asian‐Australian monsoon (AAM) and its submonsoons are investigated based on low‐emission scenario simulations using the Community Earth System Model, which are under the 1.5°C and 2.0°C warming targets proposed by the Paris Agreement. Changes in the AAM system are projected by the end of the 21st century: (1) The AAM summer precipitation at the 1.5°C warming target will increase
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Prestack seismic data interpolation and enhancement with CRS‐based migration and demigration Geophys. Prospect. (IF 1.556) Pub Date : 2021-01-25 German Garabito
The standard common‐reflection‐surface (CRS) stacking method simulates from multi‐coverage prestack data high‐quality zero‐offset stacked data and, as by‐products, provides three kinematic wavefield attributes in two dimensions that can be applied to solve reflection seismic problems. One of the most significant applications of those attributes is for interpolation and enhancement of prestack data
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Performance of BDS B1 frequency standard point positioning during the main phase of different classes of geomagnetic storms in China and its surrounding area Ann. Geophys. (IF 1.49) Pub Date : 2021-01-25 Junchen Xue; Sreeja Vadakke Veettil; Marcio Aquino; Xiaogong Hu; Lin Quan; Dun Liu
Abstract. Geomagnetic storms are one of the space weather events. The radio signals transmitted by modern navigation systems suffer from the effects of storms which can degrade the performance of the whole system. In this study, the performance of BeiDou Navigation Satellite System (BDS) B1 frequency standard point positioning in China and its surrounding area during different classes of storms is
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Study on normalization of residual displacements for single-degree-of-freedom systems Earthq. Spectra (IF 1.93) Pub Date : 2021-01-25 Zhibin Feng; Jinxin Gong
Residual displacement spectrum is one of the most important means to predict the permanent deformation of structures after the earthquake, and various normalizations of residual displacements have generally been used for construction of the spectrum. However, the issue regarding the merits and drawbacks of each normalization has not yet been investigated thoroughly. A comparison between two normalizations
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Dataset from the shake table tests of a rocking podium structure Earthq. Spectra (IF 1.93) Pub Date : 2021-01-25 Michalis F Vassiliou; Cihan Cengiz; Matt Dietz; Luiza Dihoru; Marco Broccardo; George Mylonakis; Anastasios Sextos; Bozidar Stojadinovic
Conventional validation of analytical and numerical models in Earthquake Engineering involves the comparison of numerically simulated response time histories to experimentally obtained benchmark responses to the same earthquake excitations. As the seismic design problem is inherently stochastic, an alternative, statistical, and easier-to-pass validation procedure has been suggested. As an example,
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Quantifying nuisance ground motion thresholds for induced earthquakes Earthq. Spectra (IF 1.93) Pub Date : 2021-01-25 Ryan Schultz; Vince Quitoriano; David J Wald; Gregory C Beroza
Hazards from induced earthquakes are a growing concern with a need for effective management. One aspect of that concern is the “nuisance” from unexpected ground motions, which have the potential to cause public alarm and discontent. In this article, we borrow earthquake engineering concepts to quantify the chance of building damage states and adapt them to quantify felt thresholds for induced earthquakes
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Application of discrete wavelet transform in seismic nonlinear analysis of soil–structure interaction problems Earthq. Spectra (IF 1.93) Pub Date : 2021-01-25 Reza Kamgar; Reihaneh Tavakoli; Peyman Rahgozar; Robert Jankowski
Simulation of soil–structure interaction (SSI) effects is a time-consuming and costly process. However, ignoring the influence of SSI on structural response may lead to inaccurate results, especially in the case of seismic nonlinear analysis. In this article, wavelet transform methodology has been utilized for investigation of the seismic response of soil–structure systems. For this purpose, different
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Performance of the International Monitoring System Seismic Network Based on Ambient Seismic Noise Measurements Pure Appl. Geophys. (IF 1.586) Pub Date : 2021-01-25 Peter J. Gaebler, Lars Ceranna
All nuclear explosions are banned by the Comprehensive Nuclear-Test-Ban Treaty. In the context of the treaty a verification regime was put into place to detect, locate, and characterize nuclear explosions at any time, by anyone and everywhere on the Earth. The International Monitoring System, which plays a key role in the verification regime, was set up by the Preparatory Commission of the Comprehensive
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Updates to the Regional Seismic Travel Time (RSTT) Model: 2. Path-dependent Travel-time Uncertainty Pure Appl. Geophys. (IF 1.586) Pub Date : 2021-01-25 Michael L. Begnaud, Dale N. Anderson, Stephen C. Myers, Brian Young, James R. Hipp, W. Scott Phillips
The regional seismic travel time (RSTT) model and software were developed to improve travel-time prediction accuracy by accounting for three-dimensional crust and upper mantle structure. Travel-time uncertainty estimates are used in the process of associating seismic phases to events and to accurately calculate location uncertainty bounds (i.e. event location error ellipses). We improve on the current
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Adaptive Overcomplete Dictionary Learning-Based Sparsity-Promoting Regularization for Full-Waveform Inversion Pure Appl. Geophys. (IF 1.586) Pub Date : 2021-01-25 Hongsun Fu, Yan Zhang, Xiaolin Li
Full-waveform inversion (FWI) is a highly nonlinear and ill-posed inverse problem, which needs proper regularization to produce reliable results. Recently, sparsity and overcompleteness have been successfully applied to seismic data processing. In this study, we propose a novel adaptive sparsity-promoting regularization for FWI which combines the L-BFGS algorithm with an adaptive overcomplete dictionary
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Performance of the RegCM-MITgcm Coupled Regional Model in Simulating the Indian Summer Monsoon Rainfall Pure Appl. Geophys. (IF 1.586) Pub Date : 2021-01-25 Alok Kumar Mishra, Suneet Dwivedi, Fabio Di Sante
An effort is made to evaluate the performance of an atmosphere–ocean coupled regional model in simulating the Indian summer monsoon rainfall during the years 1995–2015. The RegCM and MITgcm models are taken as the atmospheric and oceanic components of the coupled model, respectively. It is found that the coupling helps to improve the SST of the Arabian Sea and Bay of Bengal regions of the model domain
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Confirmation of AVO Attribute Inversion Methods for Gas Hydrate Characteristics Using Drilling Results from the Shenhu Area, South China Sea Pure Appl. Geophys. (IF 1.586) Pub Date : 2021-01-25 Xudong Zhang, Cheng Yin, Gulan Zhang
Amplitude versus offset (AVO) attribute inversion can help to constrain lithologies and interpret oil and gas accumulations. In this paper, we simulate four different gas hydrate and free gas configurations through AVO forward modeling. When there is no free gas under gas hydrate, the AVO attribute characteristics of gas hydrate are only related to the saturation of gas hydrate. When there is free
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Assessment of Climate Change Impacts on Drought and Wet Spells in Lake Urmia Basin Pure Appl. Geophys. (IF 1.586) Pub Date : 2021-01-25 S. Davarpanah, M. Erfanian, Kh. Javan
Drought is recognized as a natural hazard and environmental disaster, and has caused extensive impact worldwide. The increasing frequency and severity of droughts associated with global climate change is an important issue in agriculture and water resources. Given the critical situation of water resources in the Lake Urmia Basin, predicting drought characteristics in future periods is very important
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Distribution, microphysical properties, and tectonic controls of deformation bands in the Miocene subduction wedge (Whakataki Formation) of the Hikurangi subduction zone Solid Earth (IF 2.921) Pub Date : 2021-01-25 Kathryn E. Elphick; Craig R. Sloss; Klaus Regenauer-Lieb; Christoph E. Schrank
We analyse deformation bands related to horizontal contraction with an intermittent period of horizontal extension in Miocene turbidites of the Whakataki Formation south of Castlepoint, Wairarapa, North Island, New Zealand. In the Whakataki Formation, three sets of cataclastic deformation bands are identified: (1) normal-sense compactional shear bands (CSBs), (2) reverse-sense CSBs, and (3) reverse-sense
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Effect of normal stress on the frictional behavior of brucite: application to slow earthquakes at the subduction plate interface in the mantle wedge Solid Earth (IF 2.921) Pub Date : 2021-01-25 Hanaya Okuda; Ikuo Katayama; Hiroshi Sakuma; Kenji Kawai
We report the results of friction experiments on brucite under both dry and wet conditions under various normal stresses (10–60 MPa). The final friction coefficients of brucite were determined to be 0.40 and 0.26 for the dry and wet cases, respectively, independent of the normal stress. Under dry conditions, velocity-weakening behavior was observed in all experiments at various normal stresses. Under
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On the comparison of strain measurements from fibre optics with dense seismometer array at Etna volcano (Italy) Solid Earth (IF 2.921) Pub Date : 2021-01-25 Gilda Currenti; Philippe Jousset; Rosalba Napoli; Charlotte Krawczyk; Michael Weber
Abstract. We demonstrate the capability of Distributed Acoustic Sensing (DAS) in recording volcano related dynamic strain at Etna (Italy). In summer 2019, we gathered DAS measurements from a 1.5 km long fibre in a shallow trench and seismic records from a conventional dense array comprising 26 broadband sensors deployed in Piano delle Concazze close to the summit area. The multifaceted style of Etna
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Rock alteration at the post-Variscan nonconformity: implications for Carboniferous-Permian surface weathering versus burial diagenesis and paleoclimate evaluation Solid Earth (IF 2.921) Pub Date : 2021-01-25 Fei Liang; Jun Niu; Adrian Linsel; Matthias Hinderer; Dirk Scheuvens; Rainer Petschick
Abstract. A nonconformity refers to a hiatal surface located between metamorphic or igneous rocks and overlying sedimentary or volcanic rocks. Those surfaces are key features to understand the relations among climate, lithosphere and tectonic movements during ancient time. In this study, the petrological, mineralogical, and geochemical characteristics of Variscan basement rock and its overlying Permian
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Inversion of magnetic data using deep neural networks Phys. Earth Planet. Inter. (IF 2.237) Pub Date : 2021-01-16 Zhenlin Hu; Shuang Liu; Xiangyun Hu; Lihua Fu; Jie Qu; Huaijiang Wang; Qiuhua Chen
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High-pressure vibrational spectra of humite-group minerals: Fluorine effect on thermodynamic properties and hydrogen bonds Phys. Earth Planet. Inter. (IF 2.237) Pub Date : 2021-01-24 Dan Liu; Joseph R. Smyth; Xi Zhu; Yunfan Miao; Yancheng Hu; Guangchen Chen; Yu Ye
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Numerical Analysis of Shallow Foundations Resting on Granular Columns Embedded in Liquefiable Soil J. Earthq. Tsunami (IF 1.0) Pub Date : 2021-01-22 Natarajan Dinesh; Subhadeep Banerjee; Karpurapu Rajagopal
Shallow footings are the most preferred foundations for buildings due to low cost and ease of construction. However, under seismic loads, these foundations may suffer excessive settlements, particularly when there is a risk of soil liquefaction. This paper explores the effectiveness of granular columns in mitigating the liquefaction-induced ground deformations under shallow foundations, using FLAC2D
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Estimating of the b-Value Based on the Characteristic Earthquake Model J. Earthq. Tsunami (IF 1.0) Pub Date : 2021-01-22 Saman Yaghmaei-Sabegh; Gholamreza Ostadi-Asl
b-value of the Gutenberg–Richter relation as an earthquake precursor depends on the tectonic setting features. This paper presents an alternative method to calculate b-value in the presence of characteristic earthquakes. The proposed equation is based on the maximum likelihood method applied on the probability density function of the characteristic earthquake model. Data from real and simulated catalogs
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GEODETIC FAULT SLIP RATES ON ACTIVE FAULTS IN THE BAZA SUB-BASIN (SE SPAIN): INSIGHTS FOR SEISMIC HAZARD ASSESSMENT J. Geodyn. (IF 1.855) Pub Date : 2021-01-23 P. Alfaro; A. Sánchez-Alzola; I. Martin-Rojas; F.J. García-Tortosa; J. Galindo-Zaldívar; M. Avilés; A.C. López Garrido; C. Sanz de Galdeano; P. Ruano; F.J. Martínez-Moreno; A. Pedrera; M.C. Lacy; M.J. Borque; I. Medina-Cascales; A.J. Gil
One of the most significant parameters for seismic hazard assessment analyses is the fault slip rate. The combination of both geological (long-term) and geodetic (short-term) data offers a more complete characterization of the seismic potential of active faults. Moreover, geodetic data are also a helpful tool for the analysis of geodynamic processes. In this work, we present the results of a local
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High‐Frequency (6 Hz) PKPab Precursors and Their Sensitivity to Deep Earth Heterogeneity Geophys. Res. Lett. (IF 4.497) Pub Date : 2020-12-22 C. Sens‐Schönfelder; K. Bataille; M. Bianchi
We present observations on a new precursory phase of seismic waves scattered in the deep Earth. This phase arrives prior to the PKPab wave at epicentral distances larger than 155°, and we call it PKPab precursor. We show that the presence of the PKPab precursor is a necessary consequence of scattering in D″, which is the commonly accepted cause of the PKPdf precursor at distances smaller than 145°
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Deep Ductile Shear Zone Facilitates Near‐Orthogonal Strike‐Slip Faulting in a Thin Brittle Lithosphere Geophys. Res. Lett. (IF 4.497) Pub Date : 2020-12-22 Chao Liang; Jean‐Paul Ampuero; Daniel Pino Muñoz
Some active fault systems comprise near‐orthogonal conjugate strike‐slip faults, as highlighted by the 2019 Ridgecrest and the 2012 Indian Ocean earthquake sequences. In conventional Mohr‐Coulomb failure theory, orthogonal faulting requires a zero frictional coefficient (pressure‐insensitive), which is unlikely in the brittle lithosphere. The simulations developed here show that near‐orthogonal faults
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Observational Constraints on Warm Cloud Microphysical Processes Using Machine Learning and Optimization Techniques Geophys. Res. Lett. (IF 4.497) Pub Date : 2020-12-11 J. Christine Chiu; C. Kevin Yang; Peter Jan van Leeuwen; Graham Feingold; Robert Wood; Yann Blanchard; Fan Mei; Jian Wang
We introduce new parameterizations for autoconversion and accretion rates that greatly improve representation of the growth processes of warm rain. The new parameterizations capitalize on machine‐learning and optimization techniques and are constrained by in situ cloud probe measurements from the recent Atmospheric Radiation Measurement Program field campaign at Azores. The uncertainty in the new estimates
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Magnetospheric Multiscale Observations of Earth's Oblique Bow Shock Reformation by Foreshock Ultralow‐Frequency Waves Geophys. Res. Lett. (IF 4.497) Pub Date : 2020-12-19 Terry Z. Liu; Yufei Hao; Lynn B. Wilson; Drew L. Turner; Hui Zhang
Collisionless shocks can be nonstationary with periodic reformation shown in many simulation results, but direct observations are still tenuous and difficult to conclusively interpret. In this study, using Magnetospheric Multiscale (MMS) observations, we report direct observational evidence of Earth's oblique bow shock reformation driven by the foreshock Ultralow‐Frequency (ULF) waves. When the four
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Tropical Indo‐Pacific Compounding Thermal Conditions Drive the 2019 Australian Extreme Drought Geophys. Res. Lett. (IF 4.497) Pub Date : 2020-12-19 Wenjun Zhang; Wei Mao; Feng Jiang; Malte F. Stuecker; Fei‐Fei Jin; Li Qi
Australia suffered a long‐lasting extensive drought in 2019 with catastrophic wildfires creating about $4.4 billion damages, the worst record in the recent four decades. Concurrent with this extreme drought, the tropical Indo‐Pacific oceans exhibited an extraordinary combination of sea surface temperature (SST) anomalies, characterized by a Central‐Pacific (CP) El Niño event with westernmost location
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Microseismic Events Cause Significant pH Drops in Groundwater Geophys. Res. Lett. (IF 4.497) Pub Date : 2020-12-17 M. Stillings; R. J. Lunn; S. Pytharouli; Z. K. Shipton; M. Kinali; R. Lord; S. Thompson
Earthquakes cause rock fracturing, opening new flow pathways which can result in the mixing of previously isolated geofluids with differing geochemistries. Here, we present the first evidence that seismic events can significantly reduce groundwater pH without the requirement for fluid mixing, solely through the process of dynamic rock fracturing. At the Grimsel Test Site, Switzerland, we observe repeated
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The Continuum of Northeast Pacific Marine Heatwaves and Their Relationship to the Tropical Pacific Geophys. Res. Lett. (IF 4.497) Pub Date : 2020-12-19 Tongtong Xu; Matthew Newman; Antonietta Capotondi; Emanuele Di Lorenzo
Some questions remain concerning the record‐breaking 2013–2015 Northeast Pacific marine heatwave (MHW) event: was it exceptional or merely the most pronounced of a group of similar events, and was its intensity and multiyear duration driven by internal extratropical processes or did the tropics play an important role? By analyzing the statistical behavior of the historical MHWs within the ERSST.v3
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Juno Observations of Ion‐Inertial Scale Flux Ropes in the Jovian Magnetotail Geophys. Res. Lett. (IF 4.497) Pub Date : 2020-12-19 Yash Sarkango; James A. Slavin; Xianzhe Jia; Gina A. DiBraccio; Daniel J. Gershman; John E. P. Connerney; William S. Kurth; George B. Hospodarsky
Two ion‐inertial scale magnetic flux ropes are identified in the Juno magnetic field measurements in the dawnside Jovian magnetotail. Previously reported plasmoids in this region had typical diameters of several Jovian radii (RJ). However, events reported here are only ∼0.15–0.19 RJ in diameter, assuming that they move at the local Alfven speed. Using the plasma density determined by the Juno Waves
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Active north-vergent thrusting in the northern Sicily continental margin in the frame of the quaternary evolution of the Sicilian collisional system Tectonophysics (IF 3.048) Pub Date : 2021-01-19 Attilio Sulli; Maurizio Gasparo Morticelli; Mauro Agate; Elisabetta Zizzo
A three-stage evolution has characterized the Sicilian Fold and Thrust Belt (SFTB) during the last 15 My: two main thin-skinned shortening events involving mainly Meso-Cenozoic carbonate units, followed by thick-skinned thrusting involving Plio-Pleistocene deposits in the frontal area as well as the crystalline basement in the inner and deeper sector of the chain. We investigated the northern Sicily
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Accretion tectonics in Western Gondwana highlighted by the aeromagnetic signature of the Sergipano Belt, NE Brazil Tectonophysics (IF 3.048) Pub Date : 2021-01-21 Gabriela M. Almeida; Reinhardt A. Fuck; Darby P.D. de Lima; Elton L. Dantas
Identification of suture zones in Precambrian orogens can be a major problem due to later reworking and/or erosion. Interpretation of aerogeophysical data is a useful tool to the understanding of the structure and evolution of old fold belts. In this study, we use aeromagnetic data to identify domain boundaries in the Sergipano Belt (SB), a Neoproterozoic orogen developed on the northern border of
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Robust damped rank-reduction method for simultaneous denoising and reconstruction of 5D seismic data Geophysics (IF 2.609) Pub Date : 2021-01-21 Yapo Abolé Serge Innocent Oboué; Wei Chen; Hang Wang; Yangkang Chen
We have developed a new method for simultaneous denoising and reconstruction of 5D seismic data corrupted by random noise and missing traces. Several algorithms have been developed for seismic data restoration based on rank-reduction (RR) methods. More recently, a damping operator has been introduced into the conventional truncated singular-value decomposition (TSVD) formula to further remove residual
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Interpolated multichannel singular spectrum analysis: A reconstruction method that honors true trace coordinates Geophysics (IF 2.609) Pub Date : 2021-01-22 Fernanda Carozzi; Mauricio D. Sacchi
The multichannel singular spectrum analysis (MSSA) reconstruction algorithm denoises and reconstructs seismic traces on a regular grid. We have developed a modified version of MSSA that can cope with denoising and reconstruction of traces with irregular coordinates. The proposed method, interpolated multichannel singular spectrum analysis (I-MSSA), connects off-the-grid observations to the desired
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Application of the generalized finite-element method to the acoustic wave simulation in exploration seismology Geophysics (IF 2.609) Pub Date : 2021-01-22 Edith Sotelo; Marco Favino; Richard L. Gibson Jr.
The generalized finite-element method (GFEM) has been applied frequently to solve harmonic wave equations, but its use in the simulation of transient wave propagation is still limited. We have applied GFEM for the simulation of the acoustic wave equation in models relevant to exploration seismology. We also perform an assessment of its accuracy and efficiency. The main advantage of GFEM is that it
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Source-domain full-waveform inversions Geophysics (IF 2.609) Pub Date : 2021-01-21 Yulang Wu; George A. McMechan
Conventional full-waveform inversion (FWI) updates a velocity model by minimizing the data residuals between the predicted and observed data at the receiver positions. We have developed a new FWI to update the velocity model by minimizing virtual source artifacts at the receiver positions in the source-domain FWI (SFWI). Virtual source artifacts are created by replacing the propagating source wavefield
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Elastic prestack seismic inversion through discrete cosine transform reparameterization and convolutional neural networks Geophysics (IF 2.609) Pub Date : 2021-01-21 Mattia Aleardi; Alessandro Salusti
We have developed a prestack inversion algorithm that combines a discrete cosine transform (DCT) reparameterization of data and model spaces with a convolutional neural network (CNN). The CNN is trained to predict the mapping between the discrete cosine-transformed seismic data and the discrete cosine-transformed 2D elastic model. A convolutional forward modeling based on the full Zoeppritz equations
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Computational aspects of finite-frequency traveltime inversion kernels Geophysics (IF 2.609) Pub Date : 2021-01-21 Houzhu (James) Zhang; Hong Liang; Hyoungsu Baek; Yang Zhao
Finite-frequency traveltime inversion offers higher accuracy for velocity model building than ray-based traveltime inversion. The adjoint force is the key for the computation of inversion kernels. Starting at the definition of inversion kernels for the acoustic wave equation, we have derived the explicit formula for the spectral distribution density function used in the adjoint force computation. Two
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Stress-path-dependent effective medium model for granular media — Comparison with experimental data Geophysics (IF 2.609) Pub Date : 2021-01-21 Sondre Torset; Rune M. Holt
Modeling velocity changes in response to stress changes plays an important part in understanding seismic responses from the subsurface. One branch of such modeling consists of treating an assemblage of grains as an effective medium and using established grain contact theories to determine the elastic moduli. Such models are commonly limited to hydrostatic or uniaxial strain scenarios, not capable of
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VP and VS prediction from digital rock images using a combination of U-Net and convolutional neural networks Geophysics (IF 2.609) Pub Date : 2021-01-21 Rongang Cui; Danping Cao; Qiang Liu; Zhaolin Zhu; Yan Jia
Predicting elastic parameters based on digital rock images is an interesting application of a convolutional neural network (CNN), which can improve the efficiency of prediction. Predicting elastic parameters by a conventional CNN, which is used for image classification such as LeNet and AlexNet, lacks geophysical constraints, and its accuracy in predicting elastic parameters is poor, with limited training
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Microseismic denoising assessment by polarization histograms Geophysics (IF 2.609) Pub Date : 2021-01-21 German I. Brunini; Juan I. Sabbione; Julián L. Gómez; Danilo R. Velis
We have performed a comparison of microseismic data denoising methods based on their effect on the polarization attributes of 3C microseismic signals. The compared denoising methods include the classic band-pass filtering, and three recently proposed denoising techniques: restricted-domain hyperbolic Radon transform denoising, singular value decomposition (SVD)-based reduced-rank filtering, and empirical
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Detection of karst cavity beneath cast-in-place pile using the instantaneous phase difference of two receiver recordings Geophysics (IF 2.609) Pub Date : 2021-01-25 Liu Liu; Zhenming Shi; Georgios P. Tsoflias; Ming Peng; Chengcheng Liu; Fengjuan Tao; Chunsheng Liu
Karst cavities beneath bored cast in situ piles are hazardous to the stability of infrastructure projects. Therefore, it is important to detect karst cavities during the construction of piles. Downward-looking sonar deployed at the bottom of a pile hole can be used to detect cavities; however, interference of multiple reflected surface waves from the walls of the pile hole masks the weak cavity reflections
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