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This paper presented the current status of seismic noise interferometry in reconstructing the seismic velocity and discussed the four phases of data processing procedure from single-station data preparation to quality control. Each phase of the processing procedure has been discussed in detail with salient examples using seismic data acquired in Changbaishan volcano region. In the end, we used continuous recordings in Jilin, China to track the temporal changes of seismic velocity with the method introduced in this paper. We filtered the data between the frequency band 0.02 and 0.1 Hz, where the Rayleigh waves are most sensitive to the shear wave velocities in the crust and uppermost mantle. The long-term seismic variations present strong seasonal influence which may be caused by precipitation. From 2001 to 2007, the amplitude of the relative seismic velocity change increased sharply and the highest variation reached 2%, far beyond the background level. During this time, a turbulence of the magma beneath this volcano occurred. So we conclude that this anomaly of velocity was caused by the turbulence of magma. ©, 2015, State Seismology Administration. All right reserved. Source

Wei W.,China Earthquake Administration | Zhao D.,Tohoku University | Xu J.,China Earthquake Administration | Wei F.,China Earthquake Administration | Liu G.,Changbaishan Volcano Observatory
Journal of Geophysical Research B: Solid Earth | Year: 2015

We determined three-dimensional P and S wave velocities and P wave azimuthal anisotropic tomography of the Northwest Pacific subduction zones by inverting 1,225,086 P wave and 335,117 S wave arrival times from 13,413 earthquakes. Our results show some differences between P and S wave images for the stagnant Pacific slab in the mantle transition zone (MTZ) beneath Northeast China. The stagnant slab looks thicker in the P wave image than that in the S wave image, which may reflects the effects of both hydration and lower temperature in the MTZ, though differences in the resolution of P and S wave tomography may also have some effects. The Changbai intraplate volcanism is caused by hot and wet upwelling in the big mantle wedge above the stagnant Pacific slab. Our P wave anisotropy tomography shows that the fast velocity direction (FVD) in the subducting Philippine Sea plate beneath the Ryukyu arc is NE-SW (trench parallel), which is consistent with the spreading direction of the West Philippine Basin during its initial opening stage, suggesting that it may reflect the fossil anisotropy. A striking variation of the FVD with depth is revealed in the subducting Pacific slab beneath the Northeast Japan arc, which may be caused by slab dehydration that changed elastic properties of the slab with depth. The FVD in the mantle wedge beneath the Northeast Japan and Ryukyu arcs is trench normal, which reflects subduction-induced convection. Beneath the Kuril and Izu-Bonin arcs where oblique subduction occurs, the FVD in the mantle wedge is nearly normal to the moving direction of the downgoing Pacific plate, suggesting that the oblique subduction together with the complex slab morphology have disturbed the mantle flow. ©2015. American Geophysical Union. All Rights Reserved. Source

Liu J.-Q.,Jilin University | Liu J.-Q.,China Earthquake Administration | Sun J.-C.,Changbaishan Volcano Observatory | Wu C.-Z.,Changbaishan Volcano Observatory | Li K.,China Earthquake Administration
Dizhen Dizhi | Year: 2013

The active volcano-Changbaishan Tianchi Volcano in China, has an urgent eruption danger at present. There have been several eruptions in the past. In recent years, ground deformation and earthquake monitoring stations were established in the Changbaishan Volcano area, and the monitoring data show that the magma underground has triggered earthquake swarm activities and led to ground deformation. A lot of research results show that Changbaishan Tianchi Volcano is in an early unrest stage at present, the future eruption risk is increasing. The volcano disaster is very complicated. The determinants include volcano eruption pattern, crater position and magma ingredients. To the Changbaishan Tianchi Volcano, once it erupts in the future, in addition to generating volcano mud flow, debris flow and ash cloud, the flooding dam overflow caused will be the most influential and worst secondary disaster. Changbaishan Tianchi Volcano Lake is one of the highest volcano lakes in the world, with a lake area 10 km2, depth 371 m, water volume 2 billion m3, once it bursts, it will cause huge economic loss and people death to the downstream region. This article elaborates the topography and hydrology and watershed characteristics of Changbaishan Tianchi volcano. Using the hydraulic formula, we estimate the volcano lake dam-break model and analyze maximum volcano lake outburst flood flow and the flood evolution process to downstream area under the different conditions. The conclusion shows that, if the volcano lake dam collapses by half, the Er-Dao town will be flooded, and the downstream Baishan reservoir will suffer a serious threat from the floodwaters. Source

Xu J.,China Earthquake Administration | Liu G.,Changbaishan Volcano Observatory | Wu J.,Changbaishan Volcano Observatory | Wu J.,Institute of Geophysics | And 9 more authors.
Geophysical Research Letters | Year: 2012

Over 12 years of continuous monitoring of Changbaishan volcano in the border region of China and North Korea by means of volcanic seismicity, ground deformation, and volcanic gas geochemistry yields new evidence for magmatic unrest of the volcano between 2002 and 2006. In this so-called "active period," the frequency of volcanic earthquakes increased by about 2 orders of magnitude compared to that of the background "inactive periods." The active period was also accompanied by ground inflation, high values of CO 2, He, H 2, and high ratios of N 2/O 2 and 3He/ 4He in volcanic gases released from three hot springs near the caldera rim. The monitoring evidence implies pressurization of the magma chamber, possibly caused by incremental magma recharge. The ground deformation data from both GPS and precise leveling are modeled to suggest the corresponding deformation source is at 2-60 km depth beneath the volcano's summit, where earthquake swarms were detected in 2002 and 2003. Our findings suggest that the magma chamber beneath Changbaishan volcano has awakened and resumed activity after remaining dormant since AD 1903. There is an urgent need to keep close watch on this active and very hazardous volcano in northeast China. © 2012. American Geophysical Union. All Rights Reserved. Source

Ma H.R.,Jilin University | Ma H.R.,China Earthquake Administration | Yang Q.F.,Jilin University | Yang Q.F.,China Earthquake Administration | And 3 more authors.
Acta Petrologica Sinica | Year: 2015

The origin of Early Pleistocene basaltic lavas in the Erdaobaihe River basin is studied on the basis of petrochemistry and isotopic analysis. The results show that the basaltic lavas are composed of potassium trachybasalt, basaltic trachyandesite and soudium tholeiite. The lavas have similar REE patterns, suggesting that they came from the same source. The Sr, Nd and Pb isotopic tracers indicate that the magma source of the basaltic lavas is mostly close to primitive mantle. Their Mg# (= 100Mg2+/(Mg2+ + Fe2+) <60) are lower than that (= 60 ∼ 68) of the primary magma of the Early Pleistocene basalts in eastern China. Their Ni contents (27.76 × 10-6 ∼ 200.6 × 10-6) are less than that of primary mantle, whereas their Rb/Sr (0. 05 ∼ 0.09) and Ba/Rb ratios (15.64 ∼ 264) are greater than those of the primary mantle. All lines of evidence indicate that these lavas were originated from evolved magma. The parental magma is potassium trachybasaltic magma. The DI value of the lavas varies from 42 to 67, and the lavas are characterized by high Ca and Sr contents, and positive Eu anomaly in REE patterns. Trace element plots show that the basalts retain the trend of partial meting, while the trachybasalt and basaltic trachyandesite exhibit the trend of crystal fractionation. It is likely that different degree of crustal contamination has occurred during the process of magmas ascending. The Nb/Ta ratio of the basaltic rocks (14.8 ∼ 15.8) in this region is similar to that of basaltic rocks from the Kamchatka deep subduction zone. Nb/Ta-(Na2O-K2O) plots indicate that the generation of the basaltic magma is related to the partial meting of subducted slab. Source

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