A New Electronic Map of Active Faults for Southeastern Siberia O

ISSN 1028334X, Doklady Earth Sciences, 2010, Vol. 433, Part 2, pp. 1016–1021. © Pleiades Publishing, Ltd., 2010. Original Russian Text © O.V. Lunina, A.S. Gladkov, P.P. Sherstyankin, 2010, published in Doklady Akademii Nauk, 2010, Vol. 433, No. 5, pp. 662–667.

GEOLOGY

A New Electronic Map of Active Faults for Southeastern Siberia O. V. Luninaa, A. S. Gladkova, and P. P. Sherstyankinb Presented by Academician E.E. Milanovskii January 11, 2010

Received January 12, 2010

DOI: 10.1134/S1028334X10080064

One of the key problems concerning the assess The structures were considered as proved when ment of seismic hazard and regularities in the seismo they were confirmed by at least one of the following tectonic process is connected with the unavailability of direct indications: fracture zones and/or well devel electron cartographic projects, which would integrate oped (principal) system of fissures of a certain strike in various information sources at the level of advanced compact and/or poorly lithified (incoherent) rocks, technologies. The purpose of this communication seismogenic deformations, linear arrangement of consists in gathering, organizing, and critical interpre earthquake epicenters with Kp ≥ 10 along the assumed tation of geological–structural, geophysical, hydro fault, fault planes documented by underwater devices, geological, paleoseismological, and seismological data and seismoacoustic data on displacement of sedi integrated with field mapping, interpretation of topo ments. In exceptional situations, the active fault inter graphic maps (1: 200 000), digital models of the relief preted from geological–structural observations could (SRTM90), and bathymetric maps [1, 2] selected for be indistinguishable in the surface topography and the test area. Such studies in the area with coordinates river network. The indirect engineering–geological, of 100°–114° E and 50°–57° N resulted in develop hydrogeological, and geophysical indications of activ ment of a new electronic map of faults that which were ity were also used as additional criteria for substantiat active during the Neogene–Quaternary, for southeast ing the assumed fault. ern Siberia and a corresponding database, which con Most fractures in the map are oriented at 40°– tains data on known parameters of faults and indications 70° N. The minimal and maximal lengths of segments of their activity. The structure of the database was devel are 1 and 329 km, respectively. Most of the fractures oped and published earlier [3]. It should be noted that we extend for <25 km. Electronic map of the active faults used in this work the original data on >900 points of and its fragments in raster form as well as shpfailes structural–geological observations, the regional catalog presenting fault information are available at the site of earthquakes compiled at the Baikal Branch of the http://lab.crust.irk.ru/proekt/pages/maps.htm. With Geophysical Survey (Siberian Branch, Russian Academy the advent of additional information, the map of active of Sciences) (http://www.seisbukl.ru), series of maps, faults and accompanying information should be and 48 publications with descriptions of faults and neces updated in the online regime. sary corresponding information [4–15, and others]. The compiled database represents a basis for com The electronic map includes 1218 faults consisting piling (by electronic queries) maps of active faults dif of 1808 segments. Among them, 765 fractures are fering in the degree of trustworthiness (Fig. 1), kine proved and 1043 are hypothetical (Figs. 1, 2). Their matics (Fig. 2), activity degree (Fig. 3), and time of the distinct reflections in the surface topography in form last activation. The statistical parameters of complete of scarps, linear valley, or lineaments of the hydro ness of the presentday database (table) indicate that graphic network (a series of small similar elements) the amount of knowledge on active fault tectonics in were accepted as a criterion for fault defining. southeastern Siberia, as well as the interrelated geody namic processes and phenomena, is still insufficient. The available data indicate that active segments of aInstitute of the Earth’s Crust (IZK), Siberian Branch, fractures in the study test area are dominated by nor Russian Academy of Sciences, ul. Lermontova 128, Irkutsk, mal faults, with the subordinate share of downdip– 664033 Russia strikeslip and strikeslip–downdip faults. Third in bLimnological Institute, Siberian Branch, Russian Academy abundance are strikeslip faults. An insignificant share of Sciences, ul. UlanBatorskaya 3, Irkutsk, 664033 Russia of fractures is represented by reversed and updip– email: [email protected] strikeslip faults. This conclusion is natural, since

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DOKLADY EARTH SCIENCES Vol. 433 Part 2 2010 A NEW ELECTRONIC MAP OF ACTIVE FAULTS FOR SOUTHEASTERN SIBERIA 1019 1 2 3 4 5 6 7 documented ) Faults with the ) Faults 5.5 ≥

E 1–4 M ° 114 Chita ) earthquakes with 5 h the technique in [10]. ( ) weak (1–5 points); ( ) weak 4 to their activity calculated in line wit Ulan Ude ) medium (6–10 points), ( 3 ) other settlements. 7 ) regional centers, ( 6 Irkutsk ) elevated (11–20 points), ( ) elevated 2 utheastern Siberia differentiated according ) high (21–30 points), ( for the period of 1950–2009; ( 1 MONGOLIYA ° ° ° 100 N 57 50 The electronic map with active faults of so The electronic map with active by instrumental observations by instrumental observations different degrees of activity: ( Fig. 3.

DOKLADY EARTH SCIENCES Vol. 433 Part 2 2010 1020 LUNINA et al.

Statistical parameters of the completeness degree of the da area (Table 5.1 in [10]). This again indicates signifi tabase for Neogene–Quaternary faults in southeastern Si cant heterogeneity and variability of the strained crust beria (December 2009) state in fault zones. Number Share of It is of significance that the proportions of faults Characteristics of faults faults, % with different degrees of activity calculated indepen dently for southeastern Siberia (table) using the new Time of last activation database and previously estimated for its separate Historical 23 1 areas (Table 3.11 in [10]) coincide with each other. Holocene 40 2 The presentday knowledge of the area with coordi nates of 100°–114° E and 50°–57° N allows us to Quaternary 65 4 define only an insignificant share (6%) of the proved NeogeneQuaternary 1680 93 and assumed fault segments (Fig. 3) representing a Fault kinematics potential hazard with regard to tectonic, seismic, and Normal fault 328 71 engineering–geological processes, which are danger ous for the health of the population, ecology, and eco Leftlateral strikeslip–downdip fault 26 17 nomics. These are disjunctive fractures with an ele Rightlateral strikeslip–downdip fault 18 vated and high degree of activity. In other fault zones, Leftlateral downdip–strikeslip fault 23 the relative intensity of movements is substantially Rightlateral downdip–strikeslip fault 13 lower. At the same time, precisely the whole system of active fractures determines the structure of the geolog Leftlateral updip–strikeslip fault 7 2 ical medium and, consequently, its permeability for Rightlateral updip–strikeslip fault 1 fluids as well as the distribution of seismic waves, Leftlateral strikeslip–updip fault 0 anomalous geophysical fields, and dangerous natural Rightlateral strikeslip–updip fault 0 and technogenic phenomena. Leftlateral strikeslip fault 29 8 The new electronic map of active faults in south eastern Siberia may be used for different seismotec Rightlateral strikeslip fault 10 tonic and geodynamic reconstructions, applied maps Reverse fault 7 2 for prediction of dangerous natural processes related Type unclear 1346 – to crustal destruction included. Combined with the Fault activity degree database, it represents reliable grounds for gathering information, its tectonophysical analysis, and devel Minimal value in the database: 1 – – opment of other cartographic projects, which will Average value in the database: 2.95 – – allow peculiar features of the seismotectonic process Maximal value in the database: 30 – – in southeastern Siberia to be better understood. Weak (1–5 points) 1417 78 Medium (6–10 points) 289 16 ACKNOWLEDGMENTS Elevated (11–20 points) 90 5 This work was supported by the Council for Grants High (21–30 points) 12 1 of the President of the Russian Federation (grant MK Note: The activity degree of the fault segment is calculated in line 59.2009.5) and the Russian Foundation for Basic with the technique described in [10]. Research (project nos. 10050072a and 09059242 KE–EINSTEIN Consortium). most of the mapped Neogene–Quaternary faults are localized in the Baikal Rift zone. REFERENCES 1. M. De Batist, M. Canals, P. Sherstyankin, S. Alekseev, The percentage of faults with different kinematics and The INTAS Project 99–1669 Team, A New Bathy in southeastern Siberia shown in the table is consistent metric Map of Lake Baikal, Sci. Drilling Database with previously established proportions of different (2002), doi:10.1594/GFZ.SDDB.1100. stress tensors (under the condition that percentage 2. P. P. Sherstyankin, S. P. Alekseev, A. M. Abramov, et al., contributions of normal faults with extension, down Dokl. Akad. Nauk 408, 102–107 (2006) [Dokl. Earth dip–strikeslip, and strikeslip–downdip faults with Sci. 408, 564 (2006)]. extension are compared with strikeslip faults) consti 3. O. V. Lunina, A. S. Gladkov, and A. A. Gladkov, in Proc. tuting the structure of the crust strain fields in different of the 15th AllRuss. Conf. with Intern. Particip. on Geo areas of the Baikal rift zone (Table 5.1 in [10]). A sub logic Hazards (Inst. Ekol. Probl. Severa ANTs UrO stantial difference consists in the greater contribution RAN, Arkhangel’sk, 2009), pp. 288–291. of normal faults (71%, table) as compared with local 4. N. A. Logachev and K. G. Levi, Actual Questions of strain fields reflecting extension (51–57%) derived Modern Geodynamics of Central Asia (Sib. Otd. Ross. from fissuring and seismological data for the particular Akad. Nauk, Novosibirsk, 2005) [in Russian].

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