Detailed structure of the Earth’s crust and upper mantle of the Severomuysk segment of the Baikal rift zone according to teleseismic data

doi:10.13745/j.esf.sf.2022.2.1

Abstract

Abstract:

The records of distant strong earthquakes, obtained by way of a dense linear network of seismic stations in the Severomuysk segment of the Baikal rift system, revealed a complex layered-block structure of the Earth’s crust and subcrustal mantle using the longitudinal receiving function. The distribution of cross-wave velocities indicates that the properties of the blocks that make up the Severomuysk Earth’s crust differ. The western vergence of these blocks and the stratification of the lower part of the Earth’s crust confirm the accretion-collision origin of the uplift. The intensity of the collision effect on the Earth’s crust of the region is explained by the location of the Severomuysk segment on the thinned inclined edge of the Siberian Craton. A convincing correlation was found between the focal depths of earthquakes in 2015 and contrasting velocity heterogeneities in the upper part of the Earth’s crust of the Muyakan depression.

Key words: geophysics, P-receiver function, seismic velocity sections, Siberian Craton, Baikal rift zone

Valentina V. MORDVINOVA, Maria A. KHRITOVA, Elena A. KOBELEVA, Mikhail M. KOBELEV, Evgeniy Kh. TURUTANOV, Victor S. KANAYKIN. Detailed structure of the Earth’s crust and upper mantle of the Severomuysk segment of the Baikal rift zone according to teleseismic data[J]. Earth Science Frontiers, 2022, 29(2): 378-392.

Figures/Tables 9

Fig.1 Diagram of the fault structures of the Severomuysk region of the BRZ and seismicity for the period of 2014-2016. 1—epicenters of earthquakes with K ≥ 10 (M ≥ 3); 2-4—active faults: 2—interblock (I—Severo-Muysky, II—Verkhnemuysky), 3—intra-blocks (III—Perevalny, IV—Angarakansky, V— Muyakansky, VI—Yuzhnomyakansky), 4—local intra-blocks; 5—railway; 6, 7—local and regional (SVKR) seismic stations. The inset shows permanent seismic stations located at a distance of < 500 km from the activation area.

Fig.2 Epicenter density (left) and depth profile of section A-B (right) for the observation period of January 19-31, 2015. N is the average number of earthquakes on an averaging site, measured as φ = 0.01° and λ = 0.02°.

Fig.3 Three-component seismogram of the ARK station. The earthquake of February 16, 2015 off the east coast of Fr. Honshu: earthquake moment is 23:06:28; coordinates are 39.86°S, 142.88°E; magnitude M = 6.7; epicenter distance is 25.10°; depth is 23 km; backward azimuth BAZ is 118.3°.

Fig.4 Layout of seismic observations in the Severomuysk region of the BRZ. TN1, TN3, SVM, ARK, ULG—short-period stations of the temporary location network; SVKR—stationary short-period seismic station; TNV, SVM—temporary broadband stations.

Fig.5 Receiving functions of the ARK station (Q, L, T components) obtained by summing the components of the records of 16 earthquakes

Fig.6 P-receiving functions of SV waves (Q-component) for stations of the “TN1-ULG” profile. The circles indicate the variants of S-exchange at the coromancy border under the corresponding stations along the profile.

Fig.7 Velocity sections of stations of the “TN1-ULG” profile (results of inversion of the receiver function). A thin line shows the starting model, a thick line shows the restored model.

Fig.8 Two-dimensional vS-model based on the results of inversion of receiving functions and topography along the Severomuysk profile. Triangles with corresponding codes indicate the positions of seismic stations. Contours were drawn in the increments of 0.2 and 0.1 km/s in the speed ranges of 2.2-3 and 3-4.6 km/s, respectively.

Fig.9 Seismic-gravity deep section. (A) Granitoid batholith (red) and enclosing rocks (yellow). Dotted line is the boundary of the seismic profile in the density section. (B) Relief along the seismic profile. Triangles with letter codes indicate the position of seismic stations along the profile. Black line shows the isostatic anomaly of gravity. (C) Seismic-gravity deep section. Red line outlines the sole of granitoids of “batholith”. Black lines are the S-wave velocity isolines corresponding to the color velocity scale.

References 30

[1]	Aki, K., Christofferson, A., Husebye, E.S., 1977. Determination of three-demensional seismic structure of the lithosphere. Journal of Geophysical Research 82,277-296. DOI URL
[2]	Ananyin, L.V., Mordvinova, V.V., Gots’, M.F, et al., 2009. Velocity structure of the crust and upper mantle of the Baikal rift zone from long-term observations of broad-band seismic stations. Doklady Akademii Nauk 428(2), 211-214(in Russian).
[3]	Ananyin, L.V., Mordvinova, V.V., 2012. The structure of the Earth’s crust and uppermost mantle along the Baikal rift system based on teleseismic data. Doklady Earth Sciences 444(2), 721-724. DOI URL
[4]	Gao, S.S., Liu, K.H., Chen, C., 2004. Significant crustal thinning beneath the Baikal rift zone:New constraints from receiver function analysis. Geophysical Research Letters 31(20), L20610. DOI: 10.1029/2004GL020813. DOI URL
[5]	Gileva, N.A., Masalsky, O.K., Kobeleva, E.A., 2017. Epicentral region of the Muyakan sequence of earthquakes (Buryatia). The earthquakes of Russia in 2015. GS RAS, Obninsk, pp.103-107(in Russian).
[6]	Golenetsky, S.I., Kochetkov, V.M., Solonenko, A.V. et al., 1985. Geology and seismicity of BAM. Seismicity. Nauka, Novosibirsk, p.192(in Russian).
[7]	Kind, R., Kosarev, G.L., Petersen, N.V., 1995. Receiver functions at the stations of the German Regional Seismic Network (GRSN). Geophysical Journal International 121,191-202. DOI URL
[8]	Kochetkov, V.M., Borovik, N.S., Misharina, L.A., et al., 1987. Angarakansky swarm of earthquakes in the Baikal rift zone (conditions of occurrence and features of development). Nauka, Novosibirsk, p.81(in Russian).
[9]	Kosarev, G.L., Makeyeva, L.I., Vinnik, L.P., 1987. Inversion of teleseismic P-wave particle motions for crustal structure in Fennoscandia. Physics of the Earth and Planetary Interiors 47,11-24. DOI URL
[10]	Kosarev, G.L., Petersen, N.V., Vinnik, L.P., et al., 1993. Receiver functions for the Tien Shan analog broadband network: Contrast in the evolution of structures across the Talasso-Fergana fault. Journal of Geophysical Research. Part B:Soild Earth 98,(B3), 4437-4448.
[11]	Krylov, S.V., Kul’chinsky, Yu.V., 1993. Detailed seismic studies of the lithosphere on P-and S-waves. Nauka, Novosibirsk, p.199(in Russian).
[12]	Krylov, S.V., Mandelbaum, M.M., Mishenkin, B.P., et al., 1981. Earth’s interior of Baikal according to seismic data. Nauka, Novosibirsk, p.105(in Russian).
[13]	Kulakov,, I.Yu., 1999. Three-dimensional seismic heterogeneities beneath the Baikal region from data of local and teleseismic tomography. Geology and Geophysics 40(3), 317-331(in Russian).
[14]	Letnikov, F.A., 2006. Fluids in endogenic processes and problems of metallogeny. Geology and Geophysics 47 (12), 1296-1308(in Russian).
[15]	Lobkovsky, L.I., 1988. Geodinamics of spreading and subduction zones and a two-layered plate tectonics. Nauka, Moscow, p.251(in Russian).
[16]	Mandelbaum, M.M., Mishenkin, B.P., Mishenkina, Z.R., et al., 1999. Studying the South of the Siberian platform and the Baikal rift zone by deep seismic sounding. Geophysics, Spec. vol. for the 50th anniversary of “Irkutskgeofizika”, 10-21.
[17]	Mazukabzov, A.M., Donskaya, T.V., Gladkochub, D.P., et al., 2010. The Late Paleozoic geodynamics of the West Transbaikalian segment of the Central Asian fold belt. Russian Geology and Geophysics 51(5):482-491. http://dx.doi.org/10.1016/j.rgg.2010.04.008 . DOI URL
[18]	Mordvinova, V.V., Artemyev, A.A., 2010. The three-dimensional shear velocity structure of lithosphere in the southern Baikal rift system and its surroundings. Russian Geology and Geophysics 51(6), 694-707. DOI URL
[19]	Mordvinova, V.V., Deschamps, A., Dugarmaa, T., et al., 2007. Velocity structure of the lithosphere on the 2003 Mongolian-Baikal transect from SV waves. Izvestiya, Physics of the Solid Earth 43(2):119-129. http://dx.doi.org/10.1134/S1069351307020036 . DOI URL
[20]	Mordvinova, V.V., Kobelev, M.M., Treussov, A.V, et al., 2016. Deep structure of the Siberian platform - Central Asian mobile belt transition zone from teleseismic data. Geodynamics & Tectonophysica 7(1):85-103.https://doi.org/10.5800/GT-2016-7-1-0198 .
[21]	Mordvinova, V.V., Vinnik, L.P., Kosarev, G.L., et al., 2000. Teleseismic tomography of the Baikal rift lithosphere. Doklady Earth Sciences 372,716-720.
[22]	Stammler, K., 1993. SeismicHandler - programmable multichannel data handler for interactive and automating processing of seismological analyses. Computers & Geosciences 19(2), 135-140. DOI URL
[23]	Tiberi, C., Diament, M., De verche`re, J., et al., 2003. Deep structure of the Baikal rift zone revealed by joint inversion of gravity and seismology. J. Geophys. Res. 108(B3):2133. https://doi.org/10.1029/2002JB001880 .
[24]	Vinnik, L.P., 1977. Detection of waves converted from P to S in the mantle. Physics of the Earth and Planetary Interiors 15,39-45. DOI URL
[25]	Yanovskaya, T.B., Kozhevnikov, V.M., 2003. 3D S-wave velocity pattern in the upper mantle beneath the continent of Asia from Rayleigh wave data. Physics of the Earth and Planetary Interiors 138,263-278. DOI URL
[26]	Zorin,., Yu. A., 1999. Geodynamics of the western part of the Mongolia-Okhotsk collisional belt, Trans-Baikal region (Russia) and Mongolia. Tectonophysics 306,33-56. DOI URL
[27]	Zorin, Y.A., Gilewski, G.N., Golubev, V.A. et al., 1977. Essays on the deep structure of the Baikal rift, Novosibirsk, Nauka, p.153(in Russian).
[28]	Zorin, Yu.A., Kozhevnikov, V.M., Novoselova, M.R., et al., 1989. Thickness of the lithosphere beneath the Baikal rift zone and adjacent regions. Tectonophysics 168,327-337. DOI URL
[29]	Zorin, Yu.A., Mordvinova, V.V., Turutanov, E.Kh. et al., 2002. Low seismic velocity layers in the Earth’s crust beneath Eastern Siberia (Russia) and Central Mongolia: Receiver function data and their possible geological implication. Tectonophysics 359,307-327. DOI URL
[30]	Zorin, Yu.A., Turutanov, E.Kh., Mordvinova, V.V., et al., 2003 The Baikal rift zone: The effect of mantle plumes on older structure. Tectonophysics 371(1/2/3/4):153-173. http://dx.doi.org/10.1016/S0040-1951(03)00214-2 . DOI URL