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Volume 35 Issue 1 February 2022

Editor-in-Chief: Xiaodong Song

Aims and Scope

Editorial Board

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Crust and upper mantle structure of East Asia from ambient noise and earthquake surface wave tomography
Mengkui Li, Xiaodong Song, Jiangtao Li, Xuewei Bao
Accepted Manuscript , doi: 10.1016/j.eqs.2022.05.004
[Abstract](41) [FullText HTML](28) [PDF 12257KB](7)
The complex tectonic background of East Asia makes it an ideal region for investigating the evolution of the continental lithosphere, for which high-resolution lithospheric structural models are essential. In this study, we measured Rayleigh-wave phase-velocity dispersion curves at periods of 10–120 s and group velocity dispersion curves at periods of 10–140 s using event records from more than 1,000 seismic stations in and around China. By jointly inverting new and previously published dispersion data from ambient noise and earthquakes, we developed a high-resolution shear-wave velocity model down to a depth of ~300 km beneath East Asia. Our model revealed heterogeneous lithospheric structures beneath East Asia, and allowed us to investigate the velocity structure of the entire lithosphere. We also derived crustal and lithospheric thickness models from the three-dimensional (3D) shear-wave model, revealing strong spatial heterogeneity and a general thinning trend of lithospheric thickness from west to east across the study region. Overall, our models reveal important lithospheric features beneath East Asia and provide a valuable baseline dataset for understanding continental-scale dynamics and evolution.
Correlation between the tilt anomaly on the vertical pendulum at the Songpan station and the Ms 7.4 Maduo earthquake in Qinghai Province, China
Anfu Niu, Zhengyi Yuan, Jin Wei, Jing Zhao, Wei Yan
Accepted Manuscript , doi: 10.29382/Q20210053
[Abstract](3) [FullText HTML](3) [PDF 4402KB](0)
Understanding the relationship between precursory deformation anomalies and strong earthquakes is vital for physical earthquake prediction. Six months before the Ms 7.4 Maduo earthquake in Qinghai Province, China, the vertical pendulum at the Songpan station was observed to tilt southward with a high rate and large amplitude. Studies conducted before the Ms 7.4 Maduo earthquake inferred the tilt anomaly to be an earthquake precursor. However, after the earthquake, the relation between the earthquake and the anomaly became controversial, partly because the Songpan station is located at a great distance from the epicenter. In this study, based on the deformation anomaly characteristics, relationship between the seismogenic fault and the fault near the anomaly, and associated quantitative analyses, we concluded that this anomaly may be associated with the Ms 7.4 Maduo earthquake. The duration and amplitude of this anomaly matched with the magnitude and epicenter distance of the Maduo earthquake. We have also interpreted the reason why the anomaly occurred near a fault that is obliquely intersected with the seismogenic fault and why the anomaly is located far from the earthquake epicenter.
D″ anisotropy inverted from shear wave splitting intensity
Chao Zhang, Zhouchuan Huang
Accepted Manuscript , doi: 10.1016/j.eqs.2022.05.003
[Abstract](111) [FullText HTML](53) [PDF 7943KB](5)
The D″ layer, located at the bottom of the mantle, is an active thermochemical boundary layer. The upwelling of mantle plumes, as well as possible plate subduction in the D″ layer, could lead to large-scale material transformation and mineral deformation, which could result in significant seismic anisotropy. However, owing to limited observations and immense computational cost, the anisotropic structures and geodynamic mechanisms in the D″ layer remain poorly understood. In this study, we proposed a new inversion method for the seismic anisotropy in the D″ layer quantitatively with shear wave splitting intensities. We first proved the linearity of the splitting intensities under the ray-theory assumption. The synthetic tests showed that, with horizontal axes of symmetry and ray incidences lower than 30° in the D″ layer (typical SKS phase), the anisotropy is well resolved. We applied the method to the measured dataset in Africa and Western Europe, and obtained strong D″ anisotropy in the margins of the large low shear-wave velocity provinces and subducting slabs. The new method makes it possible to obtain D″ anisotropy, which provides essential constraints on the geodynamical processes at the base of the mantle.
Investigation on variations of apparent stress in the region in and around the rupture volume preceding the occurrence of the 2021 Alaska Mw 8.2 earthquake
Xuezhong Chen, Yane Li, Lijuan Chen
Accepted Manuscript
[Abstract](81) [FullText HTML](43) [PDF 5016KB](6)
On July 29, 2021, a large earthquake of Mw 8.2 occurred south of the Alaska Peninsula. To investigate the spatial–temporal changes of crustal stress in the earthquake-stricken area before this event, we selected 159 earthquakes of 4.7 ≤ Mw ≤ 6.9 that occurred in the epicentral region and its surroundings between January 1980 and June 2021 to study the temporal variation and spatial distribution of their apparent stress. In addition, we analyzed the correlation between seismic activities and Earth’s rotation and explored the seismogenic process of this earthquake. The crustal stress rose from January 2008 to December 2016. This period was followed by a sub-instability stage from January 2017 until the occurrence of the Mw 8.2 earthquake. The average rate of apparent stress change in the first five years of the stress increase period was roughly 2.3 times that in the last four years. The lateral distribution of the apparent stress shows that the areas with apparent stress greater than 1.0 MPa exhibited an expanding trend during the seismogenic process. The maximum apparent stress was located at the earthquake epicenter during the last four years. The distribution of the apparent stress in the E–W vertical cross section revealed that an apparent stress gap formed around the hypocenter during the first five years of the stress increase period, surrounded by areas of relatively high apparent stress. After the Alaska earthquake, most parts of this gap were filled in by aftershocks. The seismic activities during the sub-instability stage exhibited a significant correlation with Earth’s rotation.
A reappraisal of active faults in central-east Iran (Kerman province)
Mohammad Talebi, Abbas Sivandi-Pour, Ghasem-Ali Ahmadi, Ehsan Noroozinejad Farsangi, Shamseddin Esmaeili, Mohammad-Javad Banimahdi-Dehkordi, Hamidreza Safizadeh, Mahdieh Akbarpoor, Ehsan Ebrahimi, Rabe Sharifi Rad, Manoochehr Fallah
Accepted Manuscript , doi: 10.29382/Q20220011
[Abstract](251) [FullText HTML](114) [PDF 9600KB](21)
Fault lineaments are the main input data in earthquake engineering and seismology studies. This study presents a digitally-based active fault map of the Kerman region in central-east Iran which experienced several devastating earthquakes on poorly exposed and/or not identified active faults. Using Landsat 8 data, we have carried out the image-based procedures of fault mapping, which include applying the contrast stretching technique, the principal component analysis, the color composite technique, the spectral rationing, and creating the false-color composite images. Besides, we have cross-checked the resulting map with the geological maps provided by the Geological Survey of Iran to decrease the associated uncertainties. The resulting map includes 123 fault segments, still, a part of which has been expressed in the previously compiled active-fault maps of Iran. Indeed, the new one is mapping the poorly exposed active faults, so-called secondary faults, which are able to produce strong events. These faults are primarily associated with poorly defined areas that accommodate low levels of seismicity; however, sporadic strong events are likely to occur. It has also been investigated that these kinds of faults are seismogenic and are able to produce destructive events. In total, the outcome of this study can also be jointed with seismic studies for investigating parts of the earthquake activity in central-east Iran, in particular for the fault-based approaches in impending earthquake-resistant buildings.
High-precision relocation of the aftershock sequence of the January 8, 2022, MS6.9 Menyuan earthquake
Liping Fan, Boren Li, Shirong Liao, Ce Jiang, Lihua Fang
Accepted Manuscript , doi: 10.29382/Q20220008
[Abstract](139) [FullText HTML](68) [PDF 4371KB](28)
The 2022 Menyuan MS6.9 earthquake which occurred on January 8, 2022, is the most destructive earthquake to occur near the Lenglongling (LLL) fault since the 2016 Menyuan MS6.4 earthquake. We relocated the mainshock and aftershocks with phase arrival time observations for three days after the mainshock from the Qinghai Seismic Network using the double-difference method. The total length and width of the aftershock sequence were approximately 32 km and 5 km, respectively, and the aftershocks were mainly concentrated at a depth of 7–12 km. The relocated sequence can be divided into 18 km west and 13 km east segments with a boundary approximately 5 km east of the mainshock, where aftershocks are sparse. The east and west fault structures revealed by aftershock locations differ significantly. The west fault strikes EW and inclines to the south at a 71°–90° angle, whereas the east fault strikes 133° and has a smaller dip angle. Elastic strain accumulates at fault conjunctions with different slip rates where it is prone to large earthquakes. Based on surface traces of faults, the distribution of relocated earthquake sequence and surface ruptures, the mainshock was determined to have occurred at the conjunction of the Tuolaishan (TLS) fault and LLL fault, and the west and east segments of the aftershock sequence were on the TLS fault and LLL fault, respectively. Aftershocks migrate in the early and late stages of the earthquake sequence. In the first 1.5 h after the mainshock, aftershocks expand westward from the mainshock. In the late stage, seismicity on the northeast side of the east fault is higher than that in other regions. The migration rate of the west segment of the aftershock sequence is approximately 4.5 km/decade and the afterslip may exist in the source region.
Theoretical and quantitative evaluation of hybrid PML-ABCs for seismic wave simulation
Yuhang Wang, Wei Zhang
Accepted Manuscript , doi: 10.29382/Q20220016
[Abstract](119) [FullText HTML](67) [PDF 5950KB](5)
A good artificial boundary treatment in a seismic wave grid-based numerical simulation can reduce the size of the computational region and increase the computational efficiency, which is becoming increasingly important for seismic migration and waveform inversion tasks requiring hundreds or thousands of simulations. Two artificial boundary techniques are commonly used: perfectly matched layers (PMLs), which exhibit the best absorption performance but impose a greater computational burden by using finite layers to gradually reduce wave amplitudes; and absorbing boundary conditions (ABCs), which have the best computational efficiency but are less effective because they employ the one-way wave equation at the exterior boundary. Naturally, PMLs have been combined with ABCs to reduce the number of PMLs, thus improving the computational efficiency; many studies have proposed such hybrid PMLs. Depending on the equations from which the ABCs are derived, there are two hybrid PML variants: the PML+unstretched ABC (UABC), in which the ABC is derived from a physical equation; or the PML+stretched ABC (SABC), in which the ABC is derived from the PML equation. Even though all the previous studies concluded that hybrid PMLs can improve the absorption performance, none of them quantified how many PMLs can be removed by combining the PML with the ABC compared with the pure PML. In this paper, we systematically study the absorption performance of the two hybrid PML variants. We develop a method to distinguish the artificial reflections from the PML-interior interface and those caused by the PML exterior boundary to accurately approximate the additional absorption achieved by using the UABC and the SABC. The reflection coefficients based on a theoretical derivation and numerical tests both show that the UABC amplifies most reflections and is not recommended in any situation; conversely, the SABC can always diminish reflections, but the additional absorption achieved by the SABC is relatively poor and cannot effectively reduce the number of PMLs. In contrast, we find that simply increasing the damping parameter improves absorption better than the PML+SABC. Our results show that the improvement in absorption achieved by combining the PML with either the SABC or the UABC is not better than that obtained by simply adjusting the damping profile of the PML; thus, combining the PML with the ABC is not recommended for practice.
Seismic hazard analysis for engineering sites based on the stochastic finite-fault method
Ruifang Yu, Yisheng Song, Xiangyun Guo, Qianli Yang, Xinjuan He, Yanxiang Yu
Accepted Manuscript
[Abstract](85) [FullText HTML](45) [PDF 7157KB](9)
Seismic hazard analyses are mainly performed using either deterministic or probabilistic methods. However, there are still some defects in these statistical model-based approaches for regional seismic risk assessment affected by the near-field of large earthquakes. Therefore, we established a deterministic seismic hazard analysis method that can characterize the entire process of ground motion propagation based on stochastic finite-fault simulation, and we chose the site of the Xiluodu dam to demonstrate the method. This method can characterize earthquake source properties more realistically than other methods and consider factors such as the path and site attenuation of seismic waves. It also has high computational efficiency and is convenient for engineering applications. We first analyzed the complexity of seismogenic structures in the Xiluodu dam site area, and then an evaluation system for ground motion parameters that considers various uncertainties is constructed based on a stochastic finite-fault simulation. Finally, we assessed the seismic hazard of the dam site area comprehensively. The proposed method was able to take into account the complexity of the seismogenic structures affecting the dam site and provide multi-level parameter evaluation results corresponding to different risk levels. These results can be used to construct a dam safety assessment system of an earthquake in advance that provides technical support for rapidly and accurately assessing the post-earthquake damage state of a dam, thus determining the influence of an earthquake on dam safety and mitigating the risk of potential secondary disasters.
DiTing: A large-scale Chinese seismic benchmark dataset for artificial intelligence in seismology
Ming Zhao, Zhuowei Xiao, Shi Chen, Lihua Fang
Accepted Manuscript
[Abstract](126) [FullText HTML](84) [PDF 4692KB](20)
In recent years, artificial intelligence technology has exhibited great potential in seismic signal recognition, setting off a new wave of research. Vast amounts of high-quality labeled data are required to develop and apply artificial intelligence in seismology research. In this study, based on the 2013–2020 seismic cataloging reports of the China Earthquake Networks Center, we constructed an artificial intelligence seismological training dataset (“DiTing”) with the largest known total time length. Data were recorded using broadband and short-period seismometers. The obtained dataset included 2,734,748 three-component waveform traces from 787,010 regional seismic events, the corresponding P- and S-phase arrival time labels, and 641,025 P-wave first-motion polarity labels. All waveforms were sampled at 50 Hz and cut to a time length of 180 s starting from a random number of seconds before the occurrence of an earthquake. Each three-component waveform contained a considerable amount of descriptive information, such as the epicentral distance, back azimuth, and signal-to-noise ratios. The magnitudes of seismic events, epicentral distance, signal-to-noise ratio of P-wave data, and signal-to-noise ratio of S-wave data ranged from 0 to 7.7, 0 to 330 km, –0.05 to 5.31 dB, and –0.05 to 4.73 dB, respectively. The dataset compiled in this study can serve as a high-quality benchmark for machine learning model development and data-driven seismological research on earthquake detection, seismic phase picking, first-motion polarity determination, earthquake magnitude prediction, early warning systems, and strong ground-motion prediction. Such research will further promote the development and application of artificial intelligence in seismology.
Overview of the seismic input at dam sites in China
Houqun CHEN
Uncorrected proof
[Abstract](141) [FullText HTML](127) [PDF 4142KB](7)
The current Chinese national standard, the Standard for Seismic Design of Hydraulic Structures (GB51247), released in 2018, is strictly based on China’s national conditions and dam engineering features. A comprehensive and systematic overview of the basis of the seismic fortification requirements, the framework of the fortification criteria, and the mechanisms of seismic input related to the seismic design of dams are presented herein. We first analyzed and clarified several conceptual aspects in traditional seismic design of dams. Then, for the seismic input at the dam site described in the first national standard for hydraulic structures, we expounded innovative concepts, ideas, and methods to make relevant provisions more realistic and practical and discussed whether reservoir earthquakes must be included in the seismic fortification framework of dams. This study seeks to incorporate seismic input at the dam site into traditional seismic design practice to promote its improvement from the quasi-static method to the dynamic method and from the closed vibration system to an open wave propagation system, to ensure that the seismic design of dams becomes more reasonable, reliable, scientific, and economic.
Preface to the special issue on M6.4 Yangbi, Yunnan and M7.4 Maduo, Qinghai earthquakes
Ling Bai, Lihua Fang
Accepted Manuscript
[Abstract](200) [PDF 127KB](18)

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In Memoriam
Preface to the special memorial issue for Professor Donald V. Helmberger
Thorne Lay, Xiaodong Song
2022, 35(1): 1 -2   doi: 10.1016/j.eqs.2022.01.020
[Abstract](189) [FullText HTML](91) [PDF 1062KB](31)
Donald V. Helmberger’s art and science of waveforms
Charles A. Langston
2022, 35(1): 3 -5   doi: 10.1016/j.eqs.2022.01.001
[Abstract](208) [FullText HTML](156) [PDF 1108KB](32)
A graduate student experience with Professor Donald V. Helmberger
Thorne Lay
2022, 35(1): 6 -10   doi: 10.1016/j.eqs.2022.01.015
[Abstract](303) [FullText HTML](137) [PDF 2035KB](54)
A strange symbiosis: Seismic ray theory and Saturday touch football — Donald V. Helmberger as a graduate advisor
Terry C. Wallace
2022, 35(1): 11 -13   doi: 10.1016/j.eqs.2022.01.017
[Abstract](132) [FullText HTML](79) [PDF 1180KB](19)
Recollections of my mentor, Donald V. Helmberger
Stephen P. Grand
2022, 35(1): 14 -16   doi: 10.1016/j.eqs.2022.01.013
[Abstract](181) [FullText HTML](104) [PDF 1170KB](30)
Graduate studies with Donald V. Helmberger
John E. Vidale
2022, 35(1): 17 -18   doi: 10.1016/j.eqs.2022.01.009
[Abstract](143) [FullText HTML](82) [PDF 1073KB](25)
Memories of Donald V. Helmberger: Mentor and seismologist extraordinaire
Allison Bent
2022, 35(1): 19 -21   doi: 10.1016/j.eqs.2022.01.018
[Abstract](119) [FullText HTML](70) [PDF 1139KB](19)
How Donald V. Helmberger inspired me
Robert W. Graves
2022, 35(1): 22 -23   doi: 10.1016/j.eqs.2022.01.005
[Abstract](123) [FullText HTML](75) [PDF 1050KB](18)
Working and playing with Don: Memories of Donald V. Helmberger
David J. Wald
2022, 35(1): 24 -25   doi: 10.1016/j.eqs.2022.01.016
[Abstract](139) [FullText HTML](89) [PDF 1064KB](18)
Donald V. Helmberger memoir — exceptional seismologist, teacher, mentor, friend
Douglas Dreger
2022, 35(1): 26 -28   doi: 10.1016/j.eqs.2022.01.002
[Abstract](130) [FullText HTML](80) [PDF 1133KB](20)
Data and curiosity: Working with mentor Donald V. Helmberger
Edward Garnero
2022, 35(1): 29 -33   doi: 10.1016/j.eqs.2022.01.004
[Abstract](175) [FullText HTML](117) [PDF 1435KB](19)
My journey to the center of the Earth: A tribute to Professor Donald V. Helmberger
Xiaodong Song
2022, 35(1): 34 -39   doi: 10.1016/j.eqs.2022.01.007
[Abstract](345) [FullText HTML](114) [PDF 1401KB](26)
In memory of Donald V. Helmberger
Lupei Zhu
2022, 35(1): 40 -43   doi: 10.1016/j.eqs.2022.01.012
[Abstract](137) [FullText HTML](83) [PDF 1192KB](22)
Donald V. Helmberger the Mentor
Timothy I. Melbourne
2022, 35(1): 44 -50   doi: 10.1016/j.eqs.2022.01.019
[Abstract](148) [FullText HTML](92) [PDF 2700KB](18)
The Lost and the Found: Memories of Donald V. Helmberger
Brian Savage
2022, 35(1): 51 -53   doi: 10.1016/j.eqs.2022.01.006
[Abstract](117) [FullText HTML](88) [PDF 1064KB](17)
My seismology journey with Donald V. Helmberger
Shengji Wei
2022, 35(1): 54 -57   doi: 10.1016/j.eqs.2022.01.010
[Abstract](219) [FullText HTML](135) [PDF 1409KB](26)
Deep diving with Donald V. Helmberger
Daoyuan Sun
2022, 35(1): 58 -60   doi: 10.1016/j.eqs.2022.01.008
[Abstract](152) [FullText HTML](87) [PDF 1290KB](18)
A grand master of seismology and mentoring
Zhongwen Zhan
2022, 35(1): 61 -62   doi: 10.1016/j.eqs.2022.01.011
[Abstract](132) [FullText HTML](82) [PDF 1084KB](17)
Exploring Earth’s boundaries with Donald V. Helmberger
Voon Hui Lai
2022, 35(1): 63 -66   doi: 10.1016/j.eqs.2022.01.014
[Abstract](124) [FullText HTML](80) [PDF 1689KB](20)
Donald V. Helmberger, the master mentor: Testimonials from former international students
Xiaodong Song, Sidao Ni, Ying Tan, Alex Song, Risheng Chu, Daoyuan Sun, Shengji Wei, Semechah Lui, Voon Hui Lai
2022, 35(1): 67 -70   doi: 10.1016/j.eqs.2022.01.003
[Abstract](129) [FullText HTML](77) [PDF 1057KB](28)
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