Dense Seismic Array Research Articles

Ambient noise tomography of local shallow structure of the southern segment of Tanlu fault zone at Suqian, eastern China

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 province, where no earthquakes greater than M5.5 occurred. Fine fault zone structure could help to understand the fault activity and the potential earthquake hazards. However, only regional scale velocity model is available in this region, making it difficult to characterize detailed fault structures. In this study, we obtained local Vs model in the upper crust in this region by ambient noise tomography with a dense seismic array. For the Suqian segment, Cretaceous brittle normal faulting controlled the development of the eastern and western graben as well as the central horst between them. The graben-boundary faults are known simply as F1-F4 from east to west, and the NNE-striking fault F5 is between F1 and F2. The eastern boundary fault F1 and western boundary fault F4 separated by about 30 km are associated with intermittent high velocity anomalies in the shallow crust and are inactive. In comparison, faults F2, F5 and F3 are mainly associated with low velocity anomalies and are relatively active. These high velocity anomalies are very likely caused by the upwelling magma migrated along faults F1 and F4 in the crust, which on freezing could weld the fault zone and make it less active. Because faults F1 and F4 are hindered to move, the deformation could be transferred to nearby faults F2, F3 and F5. Our study sheds light on what controls fault activities along the TLFZ by obtaining local velocity structure in the Suqian segment.

Active-Source Interferometry in Marine and Terrestrial Environments: Importance of Directionality and Stationary Phase

ABSTRACT We utilize active-source seismic interferometry with dense seismic arrays both offshore and onland to explore the utility of this method to create virtual sources and reveal body-wave reflections in these two different environments. We first utilize data from an ocean-bottom cable (OBC) array in the Gulf of Mexico with equal numbers of sources (160 airgun shots) and receivers (160 ocean-bottom four-component sensors). We next use data from a geophone array across the Bighorn Mountains of Wyoming with many receivers (1300 vertical-component geophones) but a small number of sources (14 borehole active-source shots). We find that the OBC virtual source results, which produce strong reflections from sub-seafloor structures, are far superior to the onland results which lack usable reflections, and we explore reasons for these differences through a set of selective stacking approaches. We present techniques to account for the direction the seismic waves travel (directionality) and stationary phase and show that improvements can be made when incorporating these corrections. Although interferometric methods are based on assumptions of large numbers of widely distributed actual sources, we find that selective exclusion of potentially problematic source–receiver pairs can yield improved results. These geometric adjustments to active-source interferometry methods have utility for dense-nodal-array surveys that are now common in academic studies, but that often suffer from sparse source geometry.

Subduction of an Oceanic Plateau Across Southcentral Alaska: Scattered‐Wave Imaging

AbstractAn oceanic plateau, the Yakutat terrane, has entered the subduction system across southcentral Alaska. Its down‐dip fate and relationship to overlying volcanism is still debated. Broadband seismometers from the Wrangell Volcanism and Lithospheric Fate (WVLF) temporary experiment were deployed with <20 km spacing across southcentral Alaska to study this region. An array‐based deconvolution procedure is used to isolate the scattered P and S coda of teleseismic P waves for imaging discontinuity structure. This procedure is applied to WVLF and other dense seismic arrays across southcentral Alaska in a manner that accounts for near‐surface wavespeed variations. Two imaging techniques are employed: two‐dimensional migration and three‐dimensional common‐conversion‐point (CCP) stacking. Migrating the scattered phases along WVLF stations shows the ∼18 ± 4 km thick Yakutat crust subducting beneath the Wrangell Volcanic field to the NNE. It is offset from the Alaska‐Aleutian seismic zone laterally by 250 km to the southeast at 100 km depth, and dips more steeply (45°). At depths <45 km, CCP stacking reveals that the Yakutat crust is continuous for over 450 km along strike. This shallow continuity and deeper offset suggest a tear in the subducting Yakutat slab at depths >45 km, around 146°W. CCP stacking also reveals a continuous thin low‐velocity layer atop the underthrust Yakutat crust for >450 km along strike, at all depths <35 km. The uniform low‐velocity thrust zone indicates consistent properties through multiple rupture‐zone segments, showing that low‐velocity channels generally correspond with subduction megathrusts.

Spatiotemporal changes in seismic velocity associated with hydraulic fracturing-induced earthquakes near Fox Creek, Alberta, Canada

To characterize the subsurface geomechanical response to hydraulic fracturing (HF) activities, we study the spatiotemporal changes of seismic velocity during the completion of four HF wells in the Fox Creek area, Alberta, Canada. We estimate temporal velocity changes (dv/v) from ambient seismic noise recorded during the Tony Creek Dual Microseismic Experiment (ToC2ME) by comparing a 5-day stacked noise correlation function with a reference noise correlation function stacked over the deployment period. In the frequency band (0.1–0.4 Hz) most sensitive to the injection depths (~3.4 km), we observe daily dv/v that revealed alternating gradual velocity decreases and increases with magnitudes in the range of ±0.9%. We found a strong temporal correlation between the onset of velocity decreases and periods of intense seismicity, suggesting that the observed dv/v reductions are likely caused by stress-induced subsurface deformation due to elevated pore pressures, increased crack density, and ground shaking. A period of dv/v increase observed between the beginning and end of different well stimulation is attributed to crustal healing. Comparing the dv/v time series with injection parameters, we observed a 272.66% increase in induced seismicity and 50% more reduction in dv/v during the second injection phase that are correlated with 90.53%, 169.64%, and 4.34% increase in the injection volume, rate, and pressure, respectively. Our study provides valuable new information on the changes in reservoir elastic properties within the Western Canadian Sedimentary Basin. It also demonstrates that coda wave interferometry using data from dense seismic arrays near injection sites can be an additional tool for monitoring hydraulic fracturing operations.

Sub‐Kilometer Correlation Between Near‐Surface Structure and Ground Motion Measured With Distributed Acoustic Sensing

AbstractEarthquake ground motion depends strongly on near‐surface structure, which is challenging to image in urban areas at high resolution. Distributed acoustic sensing (DAS) is an emerging technique that provides a scalable solution by converting preexisting fiber‐optic cables into dense seismic arrays. After the July 2019 M7.1 Ridgecrest earthquake, we converted an underground dark fiber across the city of Ridgecrest, CA, into a DAS array. The recorded aftershocks show substantial lateral variability in site amplification over only 8‐km in distance. To understand the cause of such variability, we used three months of continuous data, dominated by traffic‐generated seismic noise, to image near‐surface structure along the fiber path. We find that the lateral variations of earthquake shaking correlate well with the shallow shear velocity model at sub‐kilometer scales, in particular micro‐basins filled with soft sediments. These results highlight the great potential of DAS for high‐resolution seismic hazard mapping in urban areas.

Crustal deformation of intermontane basins beneath Central Tien Shan revealed by full-wave ambient noise tomography

The Tien Shan is one of the highest, youngest, and most active orogenic belts at the southwestern margin of Central Asia. The topography of the Central Tien Shan is characterized by nearly parallel orogenic belts with interposing intermontane basins, providing an ideal site to investigate the formation and modification of the intermontane basins. Here we construct a high-resolution crustal velocity model of the Central Tien Shan using full-wave ambient noise tomography based on high-quality Rayleigh wave empirical Green's functions at periods of 5–50 s extracted from the dense seismic array during 1997–2000. Our new model reveals two high-velocity crustal anomalies beneath the Naryn Basin and Issyk-Kul Basin, respectively, and widespread low-velocity anomalies in the middle to lower crust beneath the mountain belts. We propose that the high-velocity crustal features of the Naryn Basin and Issyk-Kul Basin may be the remnant structures from the Palaeozoic collision. Widespread low-velocity anomalies reflect mantle upwelling and partial melting due to the Kazakh and Tarim lithosphere underthrusting, which have been consequently modifying the overlying crustal structures. High-resolution tomographic results reveal significant crustal heterogeneities beneath the Central Tien Shan, which shed new light on the continental growth mechanism and the crustal deformation of intermontane basins.

Ambient Noise Tomography of Upper Crustal Structures and Quaternary Faults in the Seoul Metropolitan Area and Its Geological Implications

AbstractWe investigate the upper‐crustal seismic velocity structure in the Seoul metropolitan area, where about 20 million people live. The Chugaryeong fault zone (CFZ) is placed in this area, but the seismic hazard potential remains unclear. We conducted ambient noise tomography to illuminate the high‐resolution upper‐crustal structure in the Seoul metropolitan area. We analyzed continuous vertical seismic records for ∼5 months from a dense seismic array with 77 broadband stations. Group velocity dispersion curves and tomographic maps were extracted between 0.5 and 10 s periods. We inverted 3‐D group velocity tomography models up to a depth of ∼10 km from the group velocity maps. The shear‐wave velocity model is consistent with the geological features. High‐velocity anomalies at shallow depths are correlated with the surface topography and geology. The CFZ is located at a low velocity below the 5 km depth and presented as the simplified model. The large VS contrast regions are located beneath NS‐trending faults. The cross‐sections coincide with the near‐vertical strike‐slip faults in this area. In the southern region of the Seoul metropolitan area, low‐velocity anomalies correlate with high heat flow regions. Our results effectively suggest high resolution upper‐crustal structures and subsurface hidden faults in the urban area.

Crustal Anisotropy Beneath the Trans-North China Orogen and its Adjacent Areas From Receiver Functions

As an important segment of the North China Craton, the Trans-North China Orogen (TNCO) has experienced strong tectonic deformation and magmatic activities since the Cenozoic and is characterized by significant seismicity. To understand the mechanism of the crustal deformation and seismic hazards, we determined the crustal thickness (H), Vp/Vs ratio (κ) and crustal anisotropy (the fast polarization direction φ and splitting time τ) beneath the TNCO and its adjacent areas by analyzing receiver function data recorded by a dense seismic array. The (H, κ) and (φ, τ) at a total of 309 stations were measured, respectively. The Moho depth varies from ∼30 km beneath the western margin of the Bohai bay basin to the maximum value of ∼48 km beneath the northern Lüliang Mountain, which shows the positive and negative correlations with the elevation and the Bouguer anomaly. The average φ is roughly parallel to the strikes of the faults, grabens and Mountains in this study area, whereas a rotating distribution is shown around the Datong-Hannuoba volcanic regions. Based on the φ measured from the Moho Ps and SKS/SKKS phases, we propose that the crustal deformation and seismic hazards beneath the TNCO could be due to the counterclockwise rotation of the Ordos block driven by the far-field effects of the India-Eurasian collision.

Immediate Foreshocks Indicating Cascading Rupture Developments for 527 M 0.9 to 5.4 Ridgecrest Earthquakes

AbstractUnderstanding earthquake foreshocks is essential for deciphering earthquake rupture physics and can aid seismic hazard mitigation. With regional dense seismic arrays, we identify immediate foreshocks of 527 0.9 M 5.4 events of the 2019 Ridgecrest earthquake sequence, including 48 earthquakes with series of immediate foreshocks. These immediate foreshocks are adjacent to the mainshocks occurring within 100 s of the mainshocks, and their P waves share high resemblances with the mainshock P waves. However, attributes of the immediate‐foreshock P waves, including the amplitudes and preceding times, do not clearly scale with the mainshock magnitudes. Our observations suggest that earthquake rupture may initiate in a universal fashion but evolves stochastically. This indicates that earthquake rupture development is likely controlled by fine‐scale fault heterogeneities in the Ridgecrest fault system, and the final magnitude is the only difference between small and large earthquakes.

Study on the crustal velocity structure of the Dunhua-Mishan fault based on the dense seismic array by ambient noise tomography

The Dunhua-Mishan fault is a component of the Tanlu fault zone, and it is also a major regional fault structure in Liaoning area. The study area is located in Fushun area of the Dunhua-Mishan fault. In order to study the crustal velocity structure in this region, we used 60 sets of three-component short-period seismographs and lay out two temporary profiles in Fushun, Liaoning from Nov. 3 to 25, 2019. Each temporary profiles is about 12km long that is composed of 30 seismometers, which nearly vertically cross the Dunhua-Mishan fault where the survey lines are 6km apart. The installation stations spacing distance from 200 to 400m use the external GPS time service to record frequency range of 0.2 to 150Hz in the instrument. The crustal structure characteristics of the fault zone are studied by ambient noise cross-correlation method. In order to efficiently extract high and low frequency surface wave dispersion signals at the same time, we adopt the Extended Range Phase Shift (ERPS) method. Finally, we use ERPS method to process the collected data and invert the S-wave velocity structure. We initially obtained the S-wave velocity structure of the upper crust below 5 km in the area, which matches well with the local geological data. The S-wave velocity structure has significant lateral inhomogeneity of the Dunhua-Mishan fault in Fushun area. The S-wave velocity is obviously lower on the Dunhua-Mishan fault, while with the existence of ancient mixed granite the velocity on both sides of the fault is obviously higher.

Effect of Merging Multiscale Models on Seismic Wavefield Predictions Near the Southern San Andreas Fault

AbstractUpdating Earth models used by the scientific community in geologic studies and hazard assessment has a significant societal impact but is computationally prohibitive due to the large spatial scale. The advent of urban seismology allowed rapid development of local high‐resolution models using short‐term dense seismic arrays to become conventional. To incorporate the details in these local models in community models, we developed a technique for constructing window taper functions like the cosine taper in arbitrarily shaped spatial domains on regular grids. We apply our algorithm to the problem of low‐frequency ground shaking estimation near the southernmost San Andreas fault by creating two hybrid models. These models consist of basin‐scale (top 10 km or less) high‐resolution models developed using controlled source data embedded into two popular Southern California Earthquake Center community models. We evaluate the models by computing long period (6–30 s) wavefield energy misfits using 11 earthquakes with moment magnitudes between 3.5 and 5.5 not used in developing any of the models under consideration. One of the hybrid models produces an ∼24% decrease while the other has an ∼0.6% increase in the overall median misfit relative to their original community models. The overlapping misfit values between the models and variability in waveform fit for different events and stations emphasize the difficulties in model validation. Our approach can merge any type of gridded multiscale and multidimensional datasets, and represents a valuable tool for modeling in the computational sciences.

Asthenospheric Flow Channel From Northeastern Tibet Imaged by Seismic Tomography Between Ordos Block and Yangtze Craton

AbstractThe collision between India and Eurasia forming the Tibetan Plateau since the early Cenozoic had led to the crustal and upper‐mantle (asthenospheric) extrusion from the plateau to the east. However, the Ordos and Yangtze cratonic keels next to the northeastern and eastern Tibetan Plateau obstruct this eastward asthenospheric extrusion. With a dense seismic array, for the first time, we imaged a narrow low P‐wave and S‐wave velocity anomaly characterized with higher Vp/Vs between these two Archean cratons at depths ranging from 150 to 300 km using finite‐frequency tomography. We interpret this low‐velocity anomaly as a channel of the eastward asthenospheric flow from the Tibetan Plateau. We provide solid seismic observations for a pathway of the Tibetan asthenospheric extrusion due to the ongoing collision of the Indian and Eurasian continents. This asthenospheric extrusion from the Tibetan Plateau could influence the lithospheric reworking in the central and eastern North China Craton.

Within- and Between-Event Variabilities of Strong-Velocity Pulses of Moderate Earthquakes within Dense Seismic Arrays

ABSTRACT Ground motion with strong-velocity pulses can cause significant damage to buildings and structures at certain periods; hence, knowing the period and velocity amplitude of such pulses is critical for earthquake structural engineering. However, the physical factors relating the scaling of pulse periods with magnitude are poorly understood. In this study, we investigate moderate but damaging earthquakes (Mw 6–7) and characterize ground-motion pulses using the method of Shahi and Baker (2014) while considering the potential static-offset effects. We confirm that the within-event variability of the pulses is large. The identified pulses in this study are mostly from strike-slip-like earthquakes. We further perform simulations using the frequency–wavenumber algorithm to investigate the causes of the variability of the pulse periods within and between events for moderate strike-slip earthquakes. We test the effect of fault dips, and the impact of the asperity locations and sizes. The simulations reveal that the asperity properties have a high impact on the pulse periods and amplitudes at nearby stations. Our results emphasize the importance of asperity characteristics, in addition to earthquake magnitudes for the occurrence and properties of pulses produced by the forward directivity effect. We finally quantify and discuss within- and between-event variabilities of pulse properties at short distances.

Velocity and azimuthal anisotropy structure underneath the Reelfoot Rift region from Rayleigh wave phase velocity dispersion curves

SUMMARYPhase velocity and azimuthal anisotropy maps for fundamental mode Rayleigh waves are determined for a portion of the central United States including the seismically active Reelfoot Rift (RFR) and the enigmatic Illinois Basin. Dense seismic array installations of the Northern Embayment Lithosphere Experiment, the EarthScope transportable array and the Ozarks Illinois Indiana Kentucky array allow a detailed investigation of phase velocity and anisotropy in a broad period range (20–100s).We obtain more than 12 000 well-constrained, unique two-station paths from teleseismic events. The two-station method is used to determine dispersion curves and these are inverted for isotropic phase velocity maps and azimuthal anisotropy maps for each period. The presence of fast phase velocities at lower crustal and uppermost mantle depths is found below the RFR, and Ste. Genevieve and Wabash Valley fault zones. At periods of 30s and higher, the RFR is underlain by slow phase velocities and is flanked to the NW and SE by regions of fast velocity. Fast phase velocities are present below the centre of the Illinois Basin in the period range 75–100s. Anisotropy fast axis orientations display complex patterns for each period and do not trend parallel to the direction of absolute plate motion. Anisotropy fast directions are consistently parallel to the trend of the RFR from 50s to higher periods, suggesting the presence of either frozen-in anisotropic fabric or fabric related to material transport from a recently discovered, pronounced low velocity zone below the Mississippi Embayment.

High-resolution crustal structure and gold mineralization in the southwest Cathaysia block revealed by a dense seismic array

This study presents new seismic data and interpretations for the deep structure in the southwest Cathaysia block comprised of Yunkai, Yuegui and Yuezhong blocks. A dense seismic array consisting of 112 short-period, three-component seismic stations was deployed to investigate the geodynamic mechanism of the nappe tectonic zone and gold mineralization with 2.5 km spacing across the Luoding-Yunfu region. Based on this dataset, we are able to image the high-resolution crustal structures of the southwest Cathaysia block using the P-wave receiver function method. Our imaging results reveal distinct structural features beneath the study region, including marked lateral variations of Moho discontinuities. Beneath the Luoding-Yunfu nappe tectonic zone, the Moho uplift indicates that its formation is related to deep melt mantle (e.g., Asthenospheric mantle OIB). Moho features depicted by the Ps image are different from those by the PpPs phase along this tectonic zone, which could be ascribed to the local complex structures as illustrated in the forward analysis for different Moho structures. Such a uplift is also observed from the H-κ stacking results and a low average Vp/Vs ratio (~1.65) is found in this region, which could be attributed to its location within a tectonic strain zone. Based on the analysis and comparisons with previous studies, we infer that the crustal uplift in the Luodin-Yunfu area could be a typical scenario of the ore-controlling structure. This study also suggests that upwelling channels of deep melt mantle in the southwest Cathaysia block could facilitate the progress of migration, enrichment and precipitation of gold mineralization.

Study of S‐Wave Microseisms Generated by Storms in the Southeast Australia and North Atlantic

AbstractUsing continuous data from a dense seismic array in Southwestern China, we tracked S‐wave microseism sources generated by two storms in Southeast Australia and the North Atlantic. In the frequency band 0.1–0.2 Hz, the beam strengths for SV‐ and SH‐wave sources can reach 29% and 18% of P‐wave, respectively. We found that the strong SH‐wave is only observed when the seismic sources are near the thick sedimentary regions whereas P‐ and SV‐wave is irrespective of that. It appears that in addition to a three‐dimensional structure that is needed for conversion from P‐wave to SH‐wave, amplitude enhancement by a sedimentary layer is essential for the detection of SH‐wave.

High‐Resolution Ambient Noise Imaging of Geothermal Reservoir Using 3C Dense Seismic Nodal Array and Ultra‐Short Observation

AbstractTomographic imaging based on long‐term ambient seismic noise measurements, mainly the phase information from surface waves, has been shown to be a powerful tool for geothermal reservoir imaging and monitoring. In this study, we utilize seismic noise data from a dense nodal array (192 3C nodes within 20 ) over a ultra‐short observation period (4.7 days) to reconstruct surface waves and determine the high‐resolution (0.2 km) three‐dimensional (3‐D) S wave velocity structure beneath a rural town in Zhejiang, China. We report the advantage of cross‐coherence over cross‐correlation in suppressing pseudo‐arrivals caused by persistent sources. We use ambient noise interferometry to retrieve high quality Rayleigh waves and Love waves. Body waves are also observed on the R‐R component interferograms. We apply phase velocity dispersion measurements on both Rayleigh waves and Love waves and automatically pick more than 23,000 dispersion curves by using a Machine Learning technique. 3‐D surface wave tomographic results after depth inversion indicate low‐velocity anomalies (between −1% and −4%) from the surface to 2 km depth in the central area. Combined with the conductive characteristics observed on resistivity profile, the low‐velocity anomalies are inferred to be a fluid saturated zone of highly fractured rock. Joint interpretation based on horizontal‐to‐vertical spectral ratio (HVSR) measurements, and existing temperature and fluid resistivity records observed in a nearby well, suggests the existence of the high‐temperature geothermal field through the fracture channel. Strong correlation between HVSR measurements and the S wave velocity model highlights the potential of extraction of both amplitude and phase information from ambient noise.

Depth Extent and Vp/Vs Ratio of the Chenghai Fault Zone, Yunnan, China Constrained From Dense‐Array‐Based Teleseismic Receiver Functions

AbstractFault zone (FZ) structure is critical for understanding earthquake rupture propagation and assessment of seismic hazard. In this study, we develop a new 2‐D dense‐array‐based inversion method to obtain high‐resolution FZ structure model using teleseismic receiver function. In our method, coherent travel times of converted waves and their multiples are first identified from teleseismic receiver functions; then the travel times are inverted for both depth extent and ratio beneath the seismic dense array. Synthetic tests with various shallow low‐velocity‐zone (LVZ) models demonstrate the effectiveness and robustness of our new method. We apply our method to the data recorded by a linear dense array across the southern segment of the Chenghai fault (CHF) in Yunnan, southwestern China. The inversion results suggest that the depth of the LVZ beneath the CHF extends to ∼1.1 km. Furthermore, we derive the ratio simultaneously and obtain the P‐wave velocity model from a S‐wave velocity model of the LVZ that were derived from ambient noise tomography. Travel times predicted by the newly obtained model are consistent with teleseismic P‐ and S‐wave arrivals. In addition, our method shows clear improvement in stability compared with the single‐station H‐ method. With dense seismic arrays deployed globally, our method would be a useful tool in shallow low‐velocity structure imaging studies, including fault zones and sedimentary basins.

The Seismicity of Lipari, Aeolian Islands (Italy) From One-Month Recording of the LIPARI Array

Seismic activity in volcanic settings could be the signature of processes that include magma dynamics, hydrothermal activity and geodynamics. The main goal of this study is to analyze the seismicity of Lipari Island (Southern Tyrrhenian Sea) to characterize the dynamic processes such as the interaction between pre-existing structures and hydrothermal processes affecting the Aeolian Islands. We deployed a dense seismic array of 48 autonomous 3-component nodes. For the first time, Lipari and its hydrothermal field are investigated by a seismic array recording continuously for about a month in late 2018 with a 0.1–1.5 km station spacing. We investigate the distribution and evolution of the seismicity over the full time of the experiment using self-organized maps and automatic algorithms. We show that the sea wave motion strongly influences the background seismic noise. Using an automatic template matching approach, we detect and locate a seismic swarm offshore the western coast of Lipari. This swarm, made of transient-like signals also recognized by array and polarization analyses in the time and frequency domains, is possibly associated with the activation of a NE-SW fault. We also found the occurrence of hybrid events close to the onshore Lipari hydrothermal system. These events suggest the involvement of hot hydrothermal fluids moving along pre-existing fractures. Seismological analyses of one month of data detect signals related to the regional tectonics, hydrothermal system and sea dynamics in Lipari Island.

Quaternary sodic and potassic intraplate volcanism in northeast China controlled by the underlying heterogeneous lithospheric structures

AbstractThe origin and mantle dynamics of the Quaternary intraplate sodic and potassic volcanism in northeast China have long been intensely debated. We present a high-resolution, three-dimensional (3-D) crust and upper-mantle S-wave velocity (Vs) model of northeast China by combining ambient noise and earthquake two-plane wave tomography based on unprecedented regional dense seismic arrays. Our seismic images highlight a strong correlation between the basalt geochemistry and upper-mantle seismic velocity structure: Sodic volcanoes are all characterized by prominent low seismic velocities in the uppermost mantle, while potassic volcanoes still possess a normal but thin upper-mantle “lid” depicted by high seismic velocities. Combined with previous petrological and geochemical research findings, we propose that the rarely erupted Quaternary potassic volcanism in northeast China results from the interaction between asthenospheric low-degree melts and the overlying subcontinental lithospheric mantle. In contrast, the more widespread Quaternary sodic volcanism in this region is predominantly sourced from the upwelling asthenosphere without significant overprinting from the subcontinental lithospheric mantle.