Haijiang Zhang

University of Science and Technology of China | USTC · Department of Geophysics and Planetary Sciences

We incorporate body-wave arrival time and surface-wave dispersion data into a joint inversion for three-dimensional P-wave and S-wave velocity structure of the crust surrounding the site of the San Andreas Fault Observatory at Depth. The contributions of the two data types to the inversion are controlled by the relative weighting of the respective...

Seismic imaging using ambient noise has been widely used to image subsurface structures. The spatial autocorrelation (SPAC) method using ambient noise recorded by seismic arrays can image subsurface velocity structures at various scales. In addition, an approximation of zero-offset reflection responses of the structure can be achieved by station au...

The Changning MS6.0 earthquake, occurred on June 17, 2019, is located in the southwestern margin of the Sichuan Basin. Using seismic data recorded on permanent and temporary stations around Changning area, the high-resolution three-dimensional crustal VP, VS, VP/VS models and earthquake locations in Changning-Xingwen area are obtained by using the...

To image high-resolution crustal and upper-mantle structures, ambient noise tomography (ANT) has been widely used on local and regional dense seismic arrays. One of the key steps in ANT is to extract surface-wave group and phase velocity dispersion curves from cross-correlation functions of continuous ambient noise recordings. One traditional way i...

Comparable to San Andreas fault in western United States, the Tanlu fault zone (TLFZ) is a large-scale continental tectonic belt in eastern China and has played an important role controlling the regional tectonics and earthquake activity in eastern China. It is known there exists an earthquake gap in the southern segment around Suqian, Jiangsu prov...

To take advantage of complementary strengths of earthquake body wave data and surface wave data from both earthquake and ambient noise sources, we have jointly used them to determine a high-resolution 3D Vs model of the lithosphere in South China by the joint inversion algorithm of Zhang et al. (2014). For body wave data, we assembled P- and S-wave...

Detecting subsurface fault structure is important for evaluating potential earthquake risks associated with active faults. In this study, we propose a new method to detect faults using reflected surface waves observed in ambient noise cross correlation functions. Ambient noise tomography using direct surface waves obtained from ambient noise interf...

Xin et al. (2019) presented 3D seismic velocity models (VP and VS) of crust and uppermost mantle of continental China using seismic body-wave travel-time tomography, which are referred to as Unified Seismic Tomography Models for Continental China Lithosphere 1.0 (USTClitho1.0). Compared with previous models of continental China, the VP and VS model...

Plain Language Summary Fault deformation can be characterized by the distribution of seismicity in fault zones. However, failure in the shallow crust is often aseismic due to the velocity strengthening friction behavior of fault zone materials. Isotropic velocity tomography can be used to delineate fault deformation in the aseismic or diagenetic la...

Double seismic zones are commonly observed in the subducting slabs in a global scale,serving as ideal examples for studying the seismogenetic mechanism of the intermediate-depth earthquakes. In this study, we relocate earthquakes and determine seismic velocity models using the double-difference seismic tomography method in the northern Chile subduc...

The unknown onshore extent of megathrust earthquake rupture in the Cascadia subduction zone represents a key uncertainty in earthquake hazard for the Pacific Northwest that is governed by the physical state and mechanical properties of the plate interface. The Cascadia plate interface is segmented into an interseismically locked zone located primar...

Southwest China, located at the southeastern margin of the Tibetan plateau, plays an important role for the plateau growth and its material extrusion. It has complicated tectonic environment and strong seismic activities including the 2008 Wenchuan great earthquake. Numerous geophysical studies have been conducted in southwest China. However, a com...

The Alaska Peninsula section of the Aleutian-Alaska subduction zone exhibits significant along-strike variations in plate coupling, earthquakes, and arc magmatism. Here we use regional and teleseismic data from 1990 to 2018 to investigate intermediate-depth intra-plate seismicity beneath the Alaska Peninsula. The distribution of these events shows...

The stress tensor is an important property for upper crustal studies such as those that involve pore fluids and earthquake hazards. At tectonic plate scale, plate boundary forces and mantle convection are the primary drivers of the stress field. In many local settings (10–100 s of km and <10 km depth) in tectonic plate interiors, we can simplify by...

With the development of unconventional shale gas in the southern Sichuan Basin, seismicity in the region has increased significantly in recent years. Though the existing sparse regional seismic stations can capture most earthquakes with \begin{document}$ {M}_{\mathrm{L}}\ge 2.5 $\end{document}, a great number of smaller earthquakes are often omitte...

Locating seismic events is a central task for earthquake monitoring. Compared to arrival-based location methods, waveform-based location methods do not require picking phase arrivals and are more suitable for locating seismic events with noisy waveforms. Among waveform-based location methods, one approach is to stack different attributes of P and S...

Ambient noise tomography (ANT) has become a routine method to image shear- wave velocity variations at different scales. However, ANT can only resolve smooth velocity variations and cannot give high-resolution images of the subsurface discontinuities. Here we propose a novel Transmitted Surface Wave Reverse Time Migration (TSW-RTM) method to direct...

In recent years, as the amount of seismic data has grown rapidly, it is very important to develop a fast and reliable event detection and association algorithm. Generally, event detection is first performed on individual stations followed by event association through linking phase arrivals to a common event generating them. This study considers ear...

In this study, we propose a new method to determine full moment tensor solution for induced seismicity. This method generalizes the full waveform matching algorithm we have developed to determine the double-couple (DC) focal mechanism based on the neighbourhood algorithm. One major difference between the new method and the former one is that we ado...

To better illuminate structural discontinuities around the San Andreas Fault Observatory at Depth (SAFOD) site, following the previous study of Zhang et al. (2009), we have extended the Generalized Radon Transform (GRT) method to jointly use scattered P and SH waves from abundant local earthquakes recorded by a local dense seismic network. A hybrid...

Using seismic data recorded on permanent and temporary stations around the Changning area in the Sichuan basin, the high-resolution 3D crustal VP, VS, VP/VS models and earthquake locations in the Changning–Xingwen area are obtained using the VP/VS model consistency-constrained double-difference seismic tomography method. The results show that crust...

Seismic location is an essential task for earthquake monitoring. The general practice is to locate earthquakes using arrival times from all recorded stations. However, this is not well suited for real‐time applications such as the earthquake early warning, where earthquake locations need to be determined and updated as more stations are triggered....

To better understand the upper crustal shortening and orogenic uplift in the northeastern margin of the Tibetan Plateau, we have utilized magnetotelluric (MT) data at 116 sites along two lines around the SE Gonghe Basin to determine a three-dimensional (3D) resistivity model by a 3D MT inversion package ModEM. Our resistivity model reveals a signif...

The last volcanic eruptions at the intraplate Wudalianchi volcanic field in northeast China were ∼300 yr ago. Recent ambient noise tomography (ANT) imaged a potential magma chamber beneath one of its volcanoes, the Weishan volcano, which last erupted at ca. 50 ka. To image the spatial distribution of the magmatic system and estimate the melt fracti...

In the southern Sichuan Basin, China, the recent increase in the seismic activity has been suspected to be related to hydraulic fracturing stimulation for producing the shale gas. In this study, we used the monitoring data from a local seismic network within the shale gas blocks to study the earthquakes near the shale gas production wells that have...

We present a new algorithm for derivations of 1D shear-wave velocity models from surface-wave dispersion data using convolutional neural networks (CNNs). The technique is applied for continental China and the plate boundary region in southern California. Different CNNs are designed for these two regions and are trained using theoretical Rayleigh-wa...

Seismic imaging with active seismic sources can be used to image subsurface structures such as faults, fractures, and layer interfaces with higher resolutions than tomographic methods. However, for characterizing large-scale three-dimensional structures, oftentimes it is too expensive and thus impractical to conduct active seismic survey. Seismic i...

We obtain earthquake locations and a detailed three-dimensional velocity model of the flat slab subduction zone in west-central Argentina (latitudes: 32-30°S and longitudes: 70-66°W) using a regional-scale double-difference tomography algorithm with earthquake data recorded by the SIEMBRA (2007–2009) and ESP (2008–2010) broadband seismic networks....

he source mechanism of induced seismicity by hydraulic fracture stimulation is crucial for characterizing the fracture type and local stress state. In this study, we adopted a full-waveform matching technique to determine the source mechanisms for induced seismicity. In addition to fit the waveforms of real data, this technique also matches the P-w...

Seismic tomography provides unique constraints on the morphology, the deformation, and (indirectly) the rheology of subducting slabs. We use teleseismic double-difference P-wave tomography to image with unprecedented clarity the structural complexity of the Izu-Bonin slab. We resolve a tear in the slab in the mantle transition zone (MTZ) between 26...

Ambient noise tomography (ANT) has been used successfully to image shallow earth structure. Here we perform ANT on a local dense seismic array around the Tanlu fault zone (TFZ) to the southeast of Hefei City, Anhui Province in eastern China. The array consists of 53 stations with average spacing close to 5 km. Cross-correlations of vertical-compone...

We derive high-resolution P and S seismic velocities (VP and VS) within the South-Central Transverse Ranges section of the San Andreas Fault (SAF), using a new double-difference tomography algorithm incorporating both event-pair and station-pair differential times. The addition of station-pair data allows for better absolute event locations and hig...

We propose a new wavelet-based compressive sensing method to image coseismic radiation sources with teleseismic array data. Compared to the sliding-window-based technique, our method avoids choosing the window length by taking advantages of the adaptive resolution feature of the wavelet transform. Thus artefacts caused by inappropriate window lengt...

To determine high-resolution Vp and Vs models of the lithosphere of continental China, we have assembled numerous high-quality arrival-time data from 11953 earthquakes recorded by the China Digital Seismic Network. Double-difference seismic tomography is applied to simultaneously determine earthquake locations, Vp and Vs models. Two inversion grids...

Vp/Vs models provide important complementary information to Vp and Vs models, relevant to lithology, rock damage, partial melting, water saturation, etc. However, seismic tomography using body wave traveltime data from local or regional earthquakes does not constrain Vp/Vs well due to the different resolution of Vp and Vs models, with the Vp models...

Time-lapse seismic tomography aims at obtaining temporal velocity variations of the subsurface medium in different time periods, which could be very useful for volcanic monitoring, earthquake prediction, and fault zone damage evaluation. The standard time-lapse velocity tomograms are generally obtained by subtracting velocity models resulting from...

The Gofar transform fault (GTF), 4°S on the East Pacific Rise, can generate Mw 5.5–6 earthquakes quasiperiodically on some specific patches that are separated by stationary rupture barriers. Small earthquakes along strike show a clear spatial and temporal evolution. To better understand the cause of the observed behaviors of large and small earthqu...

Based on seismic array, the conventional frequency–wavenumber method, or the FK method, is generally used to determine the backazimuth and slowness parameters for the plane wave arriving at the seismic array. However, at low frequencies the FK method results in lowresolution estimation of both parameters. To overcome this issue, we have developed a...

For seismic location and tomography, it is important to pick P- and S-wave first arrivals. However, traditional methods mainly determine P- and S-wave first arrivals separately from a signal processing perspective, which requires the extraction of waveform attributes and tuning parameters manually. Also, traditional methods suffer from noise as the...

Surface microseismic monitoring array has been widely used to monitor hydraulic fracturing process for developing unconventional oil/gas reservoirs. Here we take advantage of relatively dense surface seismic stations for monitoring the fracturing process of a shale gas reservoir in southwest China, to determine the shallow Vs structure around the f...

Induced seismicity is widely detected during hydraulic fracture stimulation and oil/gas development. To better understand how seismic events are induced, a thorough knowledge of the source mechanism is required. In this study, we have developed a new method to determine the focal mechanism for induced seismicity. Three misfit functions are used in...

Resolving both crustal and shallow-mantle heterogeneity, which is needed to study processes in and fluxes between crust and mantle, is still a challenge for seismic tomography. Body wave data can constrain deep features but often produce vertical smearing in the crust and upper mantle; in contrast, surface wave data can provide good vertical resolu...

Although global and regional seismic tomography results have revealed the presence of a mantle plume beneath Hainan Island, there is little evidence for a hotspot track associated with the Hainan plume. Here, a joint inversion of satellite gravity measurements and seismic surface wave dispersion data was performed, and the results show that a linea...

In this paper, we describe the results of a first pilot experiment of passive seismic monitoring near the active Longqi hydrothermal vent at the Southwest Indian Ridge during Chinese cruise DY115-30. During 102-day experiment, we recorded over 2,000 seismic events on a single ocean bottom seismometer with hydrophone close to the hydrothermal field....

S U M M A R Y Cross-gradient joint inversion that enforces structural similarity between different models has been widely utilized in jointly inverting different geophysical data types. However, it is a challenge to combine different geophysical inversion systems with the cross-gradient structural constraint into one joint inversion system because...

S U M M A R Y The 2015 M w 7.5 Hindu Kush earthquake occurred at a depth of 213 km beneath the Hindu Kush region of Afghanistan. While many early aftershocks were missing from the global earthquake catalogues, this sequence was recorded continuously by eight broad-band stations within 500 km. Here we use a waveform matching technique to systematica...

The tectonics of the Sunda arc region is characterized by the junction of the Eurasian and Indo‐Australian tectonic plates, causing complex dynamics to take place. High‐seismicity rates in the Indonesian region occur due to the interaction between these tectonic plates. The availability of a denser network of seismometers after the earthquakes of M...

In this expanded abstract, we report recent developments on many aspects of microseismic monitoring. For microseismic data processing and interpretation, it mainly includes four aspects: microseismic event detection, microseismic event location, microseismic event focal mechanism determination, and microseismic velocity and structure imaging. On mi...

Event detection is of vital importance for microseismic monitoring of hydraulic fracturing because of the low signal-to-noise ratio of microseismic evebts. Here we apply the so-called match and locate method (M&L) to detect weak microseismic events related to hydrofracking of a shale-gas reservoir. M&L is an effective method for small event detecti...

We proposed a potential powerful tool suitable for real-time microseismic monitoring which can obtain velocity changes immediately right after each microseismic event is recorded. This method is based on Kalman filter formulation and is a recursive travel-time inversion tool with the ability to recursively update the model covariance along with the...

Microseismic monitoring has become an essential part for unconventional oil/gas development because it provides valuable information on fracture development caused by hydraulic fracturing. However, the fracture zones characterized by location-based methods may be biased because it is subject to the completeness of detection of microseismic events....

On 25 April 2015, an Mw 7.8 earthquake occurred on the Main Himalaya Thrust fault with a dip angle of ~ 7° about 77 km northwest of Kathmandu, Nepal. This Nepal Gorkha event is the largest one on the Himalayan thrust belt since 1950. Here we use the compressive sensing method in the frequency domain to track the seismic radiation and rupture proces...