THREE-DIMENSIONAL VELOCITY STRUCTURE OF THE CRUST IN CENTRAL LAKE BAIKAL FROM LOCAL SEISMIC TOMOGRAPHY

This work deals with the importance of studying seismicity and deep structure of the Earth’s crust in the region of the Baikal rift zone. The study presents a three-dimensional velocity structure of the Earth’s crust in the central part of Lake Baikal, obtained from the results of tomographic inversion of the travel times of P- and S-waves from more than 800 seismic events. Synthetic tests provide substantiation for the resolution of the tomographic inversion algorithm. The seismic structure of the crust was obtained to a depth of 35 km and has a direct relationship with the geological structure. The three-dimensional distributions of seismic P- and S-wave velocity anomalies are in good agreement with each other.

The sharp contrast between the anomalies may indicate a difference in the material composition of the basement of the Central Baikal basin. At a 15-km depth below the Selenga River delta, there is observed a strong low-velocity anomaly which confirms the presence of a thick sedimentary cover therein. In the basement (at depths of 20 km or greater), to the northeast of the intersection between the Delta fault and the Fofanov fault, there occurs a high-velocity anomaly elongated towards the Olkhon Island. This anomaly is probably related to a rigid block in the earth’s crust. The same depths, on the western side of the Baikal-Buguldeika fault, show a reduced Vp/Vs ratio: 1.56–1.65 versus 1.70–1.75 in the adjacent areas. This indicates another type of basement rock composition and the presence of consolidated matter there.

Besides, there has been made a more accurate hypocenter determination for further comparison between seismic events and active fault structures. For the central part of Lake Baikal, the distribution of seismicity mainly corresponds to depths of 10–22 km. The situation is different below the Selenga Delta – the only area where seismicity is observed at depths greater than 22 km, – which can be attributed to complex fault interactions.

The velocity anomalies discussed herein are confined to reliably identified active faults and correlate well with the distribution of seismicity and gas hydrate structures.

1. Achauer U., Masson F., 2002. Seismic Tomography of Continental Rifts Revisited: From Relative to Absolute Het­erogeneities. Tectonophysics 358 (1–4), 17–37. https://doi.org/10.1016/S0040-1951(02)00415-8.

2. Ashurkov S.V., Sankov V.A., Miroshnichenko A.I., Lukh­nev A.V., Sorokin A.P., Serov M.A., Byzov L.M., 2011. GPS Geodetic Constraints on the Kinematics of the Amurian Plate. Russian Geology and Geophysics 52 (2), 239–249. https://doi.org/10.1016/j.rgg.2010.12.017.

3. Ashurkov S.V., Sankov V.A., Serov M.A., Luk’yanov P.Y., Grib N.N., Bordonskii G.S., Dembelov M.G., 2016. Evalua­tion of Present-Day Deformations in the Amurian Plate and Its Surroundings, Based on GPS Data. Russian Geolo­gy and Geophysics 57 (11), 1626–1634. https://doi.org/10.1016/j.rgg.2016.10.008.

4. Burkholder P.D., Meyer R.P., Delitsin L.L., Davis P.M., Zorin Yu.A., 1995. A Teleseismic Tomography Image of the Upper Mantle beneath the Southern Baikal Rift Zone. In: Proceeding of the XXI General Assembly of the Interna­tional Union of Geodesy and Geophysics (July 2–14, 1995, Boulder, Colorado, USA). IUGG, 400 p.

5. Calais E., Vergnolle M., Sankov V., Lukhnev A., Miroshni­chenko A., Amarjargal S., Déverchère J., 2003. GPS Measure­ments of Crustal Deformation in the Baikal-Mongolia Area (1994–2002): Implications on Current Kinematics of Asia. Journal of Geophysical Research: Solid Earth 108 (В10), 2501. https://doi.org/10.1029/2002JB002373.

6. Chemenda A., Déverchère J., Calais E., 2002. Three-Di­mensional Laboratory Modelling of Rifting: Application to the Baikal Rift, Russia. Tectonophysics 356 (4), 253–273. https://doi.org/10.1016/S0040-1951(02)00389-X.

7. Déverchère J., Houdry F., Diament M., Solonenko N.V., Solonenko A.V., 1991. Evidence for a Seismogenic Upper Mantle and Lower Crust in the Baikal Rift. Geophysical Re­search Letters 18 (6), 1099–1102. https://doi.org/10.1029/91GL00851.

8. Déverchère J., Petit C., Gileva N., Radziminovitch N., Mel­nikova V., Sankov V., 2001. Depth Distribution of Earth­quakes in the Baikal Rift System and Its Implications for the Rheology of the Lithosphere. Geophysical Journal In­ternational 146 (3), 714–730. https://doi.org/10.1046/j.0956-540x.2001.1484.484.x.

9. Dobretsov N.L., Buslov M.M., Vasilevsky A.N., 2019. Geo­dynamic Complexes and Structures of Transbaikalia: Re­cord in Gravity Data. Russian Geology and Geophysics 60 (3), 254–266. https://doi.org/10.15372/RGG2019021.

10. Duchkov A.D., Sokolova L.S., 2014. Heat Flow in Siberia. In: Geophysical Methods for the Study of the Earth’s Crust. Proceedings of the All-Russian Conference Dedicated to the 100th Anniversary of the Birth of Academician N.N. Puzyrev. Institute of Petroleum Geology and Geophysics, Novosibirsk, p. 211–216 (in Russian)

11. Gao S., Davis P.M., Liu H., Slack P.D., Rigor A.W., Zo­rin Y.A., Logatchev N.A., 1997. SKS Splitting beneath Con­tinental Rift Zones. Journal of Geophysical Research: Solid Earth 102 (B10), 22781–22797. https://doi.org/10.1029/97JB01858.

12. Gao S.S., Liu K.H., Davis P.M., Slack P.D., Zorin Y.A., Mor­dvinova V.V., Kozhevnikov V.M., 2003. Evidence for Small-Scale Mantle Convection in the Upper Mantle beneath the Baikal Rift Zone. Journal of Geophysical Research: Solid Earth 108 (B4), 2194. https://doi.org/10.1029/2002JB002039.

13. Gileva N.A., Melnikova V.I., Radziminovich N.A., Déver­chère J., 2000. Location of Earthquakes and Average Velocity Parameters of the Crust in Some Areas of the Baikal Region. Russian Geology and Geophysics 41 (5), 609–615.

14. Golenetsky S.I., Perevalova G.I., 1988. On the Use of Com­puters in Integrated Processing of the Data from Seismic Network in the Baikal Zone. In: A Study on the Search for Earthquake Precursors in Siberia. Nauka, Novosibirsk, p. 99–108 (in Russian)

15. Golubev V.A., 2007. Conductive and Convective Heat Transfer in the Baikal Rift Zone. GEO, Novosibirsk, 222 p. (in Russian) [Голубев В.А. Кондуктивный и конвектив­ный вынос тепла в Байкальской рифтовой зоне. Ново­сибирск: Гео, 2007. 222 с.].

16. Grudinin M.I., Chuvashova I.S (Eds), 2011. Baikal. Geolo­gy. Human. ISU Publishing House, Irkutsk, 239 p. (in Rus­sian)

17. Gvozdkov A.N., 1998. Geochemistry of the Recent Bottom Sediments of Lake Baikal. PhD Thesis (Candidate of Geology and Mineralogy). Irkutsk, 209 p. (in Russian) https://doi.org/10.1130/0091-7613(1992)020<0589:DATFOT>2.3.CO;2.

18. Khain V.E., Lomize M.G., 2005. Geotectonics with Funda­mentals of Geodynamics. University Book House, Moscow, 500 p. (in Russian)

19. Khlystov O.M., Khabuev A.V., Minami H., Hachikubo A., Krylov A.A., 2018. Gas Hydrates in Lake Baikal. Limnology and Freshwater Biology 2018 (1), 66–70. https://doi.org/10.31951/2658-3518-2018-A-1-66.

20. Khlystov O.M., Kononov E.E., Khabuev A.V., Belousov O.V., Gubin N.A., Solovyeva M.A., Naudts L., 2016. Geological and Geomorphological Characteristics of the Posolsky Bank and the Kukuy Griva, Lake Baikal. Russian Geology and Geo­physics 57 (12), 1759–1767. https://doi.org/10.1016/j.rgg.2016.11.001.

21. Koulakov I., 2009. LOTOS Code for Local Earthquake Tomographic Inversion: Benchmarks for Testing Tomogra­phic Algorithms. Bulletin of the Seismological Society of America 99 (1), 194–214. https://doi.org/10.1785/0120080013.

22. Koulakov I., Tychkov S., Bushenkova N., Vasilevsky A., 2002. Structure and Dynamics of the Upper Mantle beneath the Alpine–Himalayan Orogenic Belt, from Teleseismic To­mography. Tectonophysics 358 (1–4), 77–96. https://doi.org/10.1016/S0040-1951(02)00418-3.

23. Krylov S.V., 1980. On Depths of the Baikal Earthquakes and Factors Controlling Seismicity. Russian Geology and Geophysics 5, 97–112 (in Russian)

24. Kulakov I.Yu., 1999. Three-Dimensional Seismic Hetero­geneities beneath the Baikal Region According to Data of Local Teleseismic Tomography. Russian Geology and Geo­physics 40 (3), 317–331 (in Russian)

25. Kulakov I.Yu., 2008. Upper Mantle Structure beneath Southern Siberia and Mongolia, from Regional Seismic To­mography. Russian Geology and Geophysics 49 (3), 187–196. https://doi.org/10.1016/j.rgg.2007.06.016.

26. Lesne O., Calais E., Deverchère J., Chéry J., Hassani R., 2000. Dynamics of Intracontinental Extension in the North Baikal Rift from Two-Dimensional Numerical Deformation Modeling. Journal of Geophysical Research: Solid Earth 105 (B9), 21727–21744. https://doi.org/10.1029/2000JB900139.

27. Levi K.G., Babushkin S.M., Badardinov A.A., Buddo V.Y., Larkin G.V., Miroshnichenko A.I., Colman S., 1995. Active Baikal Tectonics. Russian Geology and Geophysics 36 (10), 143–154.

28. Levi K.G., Miroshnichenko A.I., Sankov V.A., Babush­kin S.M., Larkin G.V., Badardinov A.A., Wong H.K., Colman S., Delvaux D., 1997. Active Faults of the Baikal Depression. Bulletin des Centres de Recherches Elf Exploration Produc­tion 21 (2), 399–434.

29. Logachev N.A., 1974. The Sayan-Baikal and Stanovoe Highlands. In: N.A. Florensov (Ed.), Highlands of Pribaikalie and Transbaikalia. Nauka, Moscow, p. 16–162 (in Russian)

30. Logatchev N.A., 1993. History and Geodynamics of the Lake Baikal Rift in the Context of the Eastern Siberia Rift System: A Review. Bulletin des Centres de Recherches Elf Exploration Production 17 (2), 353–370.

31. Logachev N.A., 1999. Main Structural Features and Geo­dynamics of the Baikal Rift Zone. Physical Mesomechanics 2 (1–2), 163–170 (in Russian)

32. Logachev N.A., 2001. On Historical Core of the Baikal Rift Zone. Doklady Earth Sciences 376 (4), 510–513 (in Russian)

33. Logachev N.A., 2003. History and Geodynamic of the Baikal Rift. Russian Geology and Geophysics 44 (5), 391–406.

34. Logatchev N.A., Zorin Yu.A., 1987. Evidence and Causes of the Two-Stage Development of the Baikal Rift. Tectono­physics 143 (1–3), 225–234. https://doi.org/10.1016/0040-1951(87)90092-8.

35. Lukhnev A.V., Sankov V.A., Miroshnichenko A.I., Ashur­kov S.V., Byzov L.M., Sankov A.V., Bashkuev Yu.B., Dem­belov M.G., Calais E., 2013. GPS-Measurements of Recent Crustal Deformation in the Junction Zone of the Rift Seg­ments in the Central Baikal Rift System. Russian Geology and Geophysics 54 (11), 1417–1426. https://doi.org/10.1016/j.rgg.2013.10.010.

36. Lunina O.V., 2016. The Digital Map of the Pliocene–Qua­ternary Crustal Faults in the Southern East Siberia and the Adjacent Northern Mongolia. Geodynamics & Tectonophysics 7 (3), 407–434 (in Russian) https://doi.org/10.5800/GT-2016-7-3-0215.

37. Lunina O.V., Andreev A.V., Gladkov A.S., 2012. The Tsagan Earthquake of 1862 on Lake Baikal Revisited: A Study of Secondary Coseismic Soft-Sediment Deformation. Russian Geology and Geophysics 53 (6), 594–610. https://doi.org/10.1016/j.rgg.2012.04.007.

38. Lunina O.V., Gladkov A.S., Nevedrova N.N., 2009. Rift Basins in Pribaikal’e: Tectonic Structure and Development History. GEO, Novosibirsk, 316 p. (in Russian)

39. Lunina O.V., Gladkov A.S., Sherstyankin P.P., 2010. A New Electronic Map of Active Faults for Southeastern Siberia. Doklady Earth Sciences 433, 1016–1021. https://doi.org/10.1134/S1028334X10080064.

40. Mats V.D., 2012. The Sedimentary Fill of the Baikal Basin: Implications for Rifting Age and Geodynamics. Russian Ge­ology and Geophysics 53 (9), 936–954. https://doi.org/10.1016/j.rgg.2012.07.009.

41. Mats V.D., 2015. The Baikal Rift: Pliocene (Miocene) – Quarternary Episode or Product of Extended Development since the Late Cretaceous under Various Tectonic Factors. A Review. Geodynamics & Tectonophysics 6 (4), 467–490 (in Russian) https://doi.org/10.5800/GT-2015-6-4-0190.

42. Mats V.D., Ufimtsev G.F., Mandelbaum M.M., Alakshin A.M., Pospeev A.V., Shimaraev M.N., Khlystov O.M., 2001. The Ce­nozoic Baikal Rift Basin: Its Structure and Geological His­tory. GEO, Novosibirsk, 252 p. (in Russian)

43. Melnikova V.I., Radziminovich N.A., 1998. Focal Mecha­nisms of the Earthquakes of the Baikal Region for 1991–1996. Russian Geology and Geophysics 39 (11), 1598–1607 (in Russian)

44. Misharina L.A., Melnikova V.I., Baljinnyam I., 1983. South­western Boundary of the Baikal Rift Zone from the Data on Earthquake Focal Mechanisms. Volcanology and Seis­mology 2, 74–83 (in Russian)

45. Misharina L.A., Solonenko N.V., 1972. On Stresses at Small Earthquake Sources in Pribaikalye. Bulletin of the USSR Academy of Sciences. Physics of the Earth 4, 24–36 (in Rus­sian)

46. Misharina L.A., Solonenko N.V., 1977. Earthquake Focal Mechanisms and Stressed State of the Earth’s Crust in the Baikal Rift Zone. In: N.A. Logachev, N.A. Florensov (Eds),

47. A Role of Rifting in Geological History of the Earth. Nauka, Novosibirsk, p. 120–125 (in Russian)

48. Mordvinova V.V., Vinnik L.P., Kosarev G.L., Oreshin S.I., Treusov A.V., 2000. Teleseismic Tomography of the Baikal Rift Lithosphere. Doklady Earth Sciences 372 (4), 716–720.

49. Nevedrova N.N., Epov M.I., 2004. Analysis of Electro­magnetic Monitoring Results at Baikal Prognostic Test-Site. NNC RK Bulletin 2, 143–149 (in Russian)

50. Nicolas A., Achauer U., Daignieres M., 1994. Rift Initia­tion by Lithospheric Rupture. Earth and Planetary Science Letters 123 (1–3), 281–298. https://doi.org/10.1016/0012-821X(94)90274-7.

51. Nolet G. (Ed.), 1990. Seismic Tomography. With Ap­plications in Global Seismology and Explorational Geo­physics. Mir, Moscow, 416 p. (in Russian)

52. Peltzer G., Tapponnier P., 1988. Formation and Evolu­tion of Strike-Slip Faults, Rifts, and Basins during the India-­Asia Collision: An Experimental Approach. Journal of Geo­physical Research: Solid Earth 93 (B12), 15085–15117. https://doi.org/10.1029/JB093iB12p15085.

53. Petit C., Koulakov I., Deverchère J., 1998. Velocity Struc­ture around the Baikal Rift Zone from Teleseismic and Lo­cal Earthquake Traveltimes and Geodynamic Implications. Tectonophysics 296 (1–2), 125–144. https://doi.org/10.1016/S0040-1951(98)00140-1.

54. Radziminovich N.A., 2010. Focal Depths of Earthquakes in the Baikal Region: A Review. Izvestiya, Physics of the Solid Earth 46, 216–229. https://doi.org/10.1134/S1069351310030043.

55. Sankov V.A., Lukhnev A.V., Miroshnichenko A.I., Levi K.G., Ashurkov S.V., Bashkuev Yu.B., Dembelov M.G., Calais E., Déverchère J., Vergnolle M., Bechtur B., Amarjargal Ch., 2003. Present-Day Movements of the Earth’s Crust in the Mongol-Siberian Region Inferred from GPS Geodetic Data. Reports of the Academy of Sciences 393 (8), 1082–1085.

56. Scholz C.A., Hutchinson D.R., 2000. Stratigraphic and Structural Evolution of the Selenga Delta Accommodation Zone, Lake Baikal Rift, Siberia. International Journal of Earth Sciences 89, 212–228. https://doi.org/10.1007/s005310000095.

57. Shchetnikov A.A., Radziminovich Y.B., Vologina E.G., Ufim­tsev G.F., 2012. The Formation of Proval Bay as an Episode in the Development of the Baikal Rift Basin: A Case Study. Geomorphology 177–178, 1–16. http://doi.org/10.1016/j.geomorph.2012.07.023.

58. Sherman S.I., Levi K.G., 1977. Transform Faults of the Baikal Rift Zone. Doklady of the USSR Academy of Sciences 233 (2), 461–464 (in Russian)

59. Sherman S.I., Lysak S.V., Gorbunova E.A., 2012. A Tec­tonophysical Model of the Baikal Seismic Zone: Testing and Implications for Medium-Term Earthquake Prediction. Russian Geology and Geophysics 53 (4), 392–405. https://doi.org/10.1016/j.rgg.2012.03.003.

60. Solonenko V.P. (Ed.), 1981. Seismogeology and Detailed Seismic Zoning of Pribaikalye. Nauka, Novosibirsk, 168 p. (in Russian)

61. Song Y., Krylov S.V., Yang B., Cai L., Dong S., Liang T., Li J., Xu X., Mishenkina Z.R., Petrik G.V., Shelud’ko I.F., Se­leznev V.S., Solov’ev V.M., 1996. Deep Seismic Sounding of the Lithosphere on the Baikal – Northeastern China Inter­national Transect. Russian Geology and Geophysics 37 (2), 3–15 (in Russian)

62. State Geological Map of the Russian Federation, 2009. Angara-Yenisei Series. Scale 1:1000000. Sheet N-48 (Irkutsk). Explanatory Note. VSEGEI Publishing House, Saint Peters­burg, 574 p. (in Russian)

63. Suvorov V.D., Mishen’kina Z.R., 2005. Structure of Sedi­mentary Cover and Basement beneath the South Basin of Lake Baikal Inferred from Seismic Profiling. Russian Geolo­gy and Geophysics 46 (11), 1141–1149.

64. Suvorov V.D., Tubanov T.A., 2008. Distribution of Local Earthquakes in the Crust beneath Central Lake Baikal. Rus­sian Geology and Geophysics 49 (8), 611–620. http://doi.org/10.1016/j.rgg.2007.09.019.

65. Ten Brink U.S., Taylor M.H., 2002. Crustal Structure of Central Lake Baikal: Insights into Intracontinental Rifting. Journal of Geophysical Research: Solid Earth 107 (B7), 2132. https://doi.org/10.1029/2001JB000300.

66. Tiberi C., Diament M., Déverchère J., Petit-Mariani C., Mikhailov V., Tikhotsky S., Achauer U., 2003. Deep Struc­ture of the Baikal Rift Zone Revealed by Joint Inversion of Gravity and Seismology. Journal of Geophysical Research: Solid Earth 108 (B3), 2133. http://doi.org/10.1029/2002jb001880.

67. Yakovlev A.V., Koulakov I.Yu., Tychkov S.A., 2007. Moho Depths and Three-Dimensional Velocity Structure of the Crust and Upper Mantle beneath the Baikal Region, from Local Tomography. Russian Geology and Geophysics 48 (2), 204–220. http://doi.org/10.1016/j.rgg.2007.02.005.

68. Zhao D., Lei J., Inoue T., Yamada A., Gao S.S., 2006. Deep Structure and Origin of the Baikal Rift Zone. Earth and Plane­tary Science Letters 243 (3–4), 681–691. https://doi.org/10.1016/j.epsl.2006.01.033.

69. Zonenshain L.P., Savostin L.A., 1981. Geodynamics of the Baikal Rift Zone and Plate Tectonics of Asia. Tectono­physics 76 (1–2), 1–45. https://doi.org/10.1016/0040-1951(81)90251-1.

70. Zorin Yu.A., Turutanov E.Kh., 2005. Plumes and Geody­namics of the Baikal Rift Zone. Russian Geology and Geo­physics 46 (7), 685–699 (in Russian)