Valērijs Ņikuļins SEISMICITY OF THE EAST BALTIC REGION AND APPLICATION-ORIENTED METHODS IN THE CONDITIONS OF LOW SEISMICITY Valērijs Ņikuļins SeiSmicity of the eaSt Baltic Region and application-oRiented methodS in the conditionS of low SeiSmicity lU akadēmiskais apgāds 2017 Ņikuļins Valērijs, 2017. Seismicity of the East Baltic Region and application-oriented methods in the conditions of low seismicity. Rīga: LU Akadēmiskais apgāds, pp. 292. Monograph is dedicated to seismicity of the East Baltic region and its assessment. As the first study of its kind, it is published in English language to ensure accessibility of the facts and methodological solutions reflected in the book to the readership worldwide. Most of the factual material included in the study is published for the first time, and a particularly valuable contribution of the book includes the methodological techniques developed and approbated by the author for assessing seismicity of the territories. These are novelties that the author presents in a relatively simple language, providing explanations on the basis of traditional notions and seismic observation network data. The book is intended for geologists and geophysicists, territorial planning specialists, builders, as well as other individuals, whom this edition will enable to become familiar with this specific knowledge regarding Latvia and its neighboring countries. This information is also important in extraction of mineral resources and planning thereof, where artificially induced seismic events are a factor with a significant environmental impact. Monogrāfija ir veltīta Austrumbaltijas reģiona seismiskumam un tā novērtējumiem, tas ir pirmais šāds pētījums, tādēļ sagatavots angļu valodā, lai grāmatā atspoguļotais faktiskais materiāls un metodiskie risinājumi kļūtu pieejami plašam lasītāju lokam. Grāmatā ietvertā faktiskā materiāla lielākā daļa ir oriģināli un tiek publicēti pirmo reizi, un īpaši vērtīgu šo izdevumu izceļ autora paša izstrādātie un aprobētie metodiskie paņēmieni teritoriju seismiskuma izvērtēšanai. Tās ir novitātes, kuras autors pasniedz salīdzinoši vienkāršā valodā, skaidrojumus balstot uz tradicionāliem priekšstatiem un seismisko novērojumu tīklu datiem. Grāmata paredzēta ģeologiem un ģeofiziķiem, tomēr vēl vairāk teritoriju plānotājiem, būvniekiem, kā arī citiem interesentiem, kam šādas zināšanas par Latviju un kaimiņzemēm ar šo izdevumu ir kļuvušas pieejamas. Svarīgi tas ir arī attiecībā uz derīgo izrakteņu ieguvi un tās plānošanu, kur mākslīgi ierosināti seismiskie notikumi ir nozīmīgs vidi ietekmējošs faktors. Editor in Chief / Atbildīgais redaktors: Dr. geol. Valdis Segliņš This publication was financially supported by the National Research Programme “ResProd” No. 2014.10-4/VPP-6/4.1 project "GEO"/ Izdevums tapis ar Valsts pētījumu programmas “ResProd” Nr. 2014.10-4/VPP-6/4 1. projekta "GEO" atbalstu. Editor / Redaktore: Andra Damberga Computer graphics and design / Datorgrafika un dizains: Paula Lore Cover design / Vāka dizains: Paula Lore © Valērijs Ņikuļins, 2017 © Latvijas Universitāte, 2017 ISBN 978-9934-18-300-3 content Introduction ............................................................................................................. 7 1. Earth’s seismicity and its causes ........................................................................ 14 1.1. Depth tectonic structure of Earth and geodynamic preconditions of seismicity ............................................................................... 14 1.2. Statistics of world earthquakes ......................................................................... 21 2. Seismicity and prerequisites of seismicity of stable continental regions ....... 28 2.1. Review of seismic geological conditions of stable continental crust .......... 30 2.2. Brief description of geotectonic conditions of the East European Platform and its individual elements .............................................................. 41 2.2.1. Overview of evolutionary processes of the formation of East European Platform and main elements of its geological structure .......................................................................... 43 2.2.2. Deep geological structure of western part of the East European Platform ........................................................................ 48 2.2.3. Assessment of geodynamic potential of the East Baltic Region ..... 54 2.3. Basic characteristics of the EEP seismicity .................................................... 58 3. Seismicity of the East Baltic Region ................................................................. 64 3.1. History of seismological studies in the East Baltic Region .......................... 64 3.1.1. Seismologic data collection period from the earliest times to the end of XIX century .......................................................... 65 3.1.2. Seismological studies until mid-70s of XX century .......................... 65 3.1.3. Seismological studies from mid-70s of XX century to 2004 ........... 69 3.1.4. Current stage of seismological studies in the East Baltic Region .................................................................................. 74 3.2. Historical earthquakes in the East Baltic region ........................................... 77 3.2.1. Earthquakes in East Prussia in 1302 and 1328 .................................. 78 3.2.2. Bauska earthquake of 30 June 1616 ..................................................... 78 3.2.3. Koknese earthquakes of 1821 ............................................................... 79 3.2.4. Irbene earthquake of 18 May 1857 ...................................................... 82 3.2.5. Narva earthquake of 1881 ..................................................................... 82 3.2.6. Sesmic shocks in December 1908 in the East Baltic Region ........... 83 3.3. Present-day earthquakes of East Baltic Region ............................................. 86 3.3.1. Osmussaare earthquakes of 1976 ......................................................... 87 3.3.2. Kaliningrad earthquakes of 2004 ......................................................... 91 4 3.3.3. Review of contemporary, small earthquakes of the East Baltic Region ............................................................................ 99 4. Technogenic seismicity and tectonic earthquake identification methods in the East Baltic Region .................................................................... 105 4.1. Models, mechanisms of seismic sources and tectonic regimes ................... 107 4.1.1. Focal mechanism of tectonic earthquake ........................................... 108 4.1.2. Tectonic regimes .................................................................................... 110 4.1.3. Seismic moment tensor ......................................................................... 112 4.1.4. Model of explosion ................................................................................ 114 4.2. Technogenic seismicity in East Baltic Region ............................................... 116 4.2.1. Technogenic seismicity of Estonia ....................................................... 125 4.2.2. Technogenic seismicity of Latvia ......................................................... 130 4.2.3. Technogenic seismicity of Lithuania ................................................... 133 4.2.4. Technogenic seismicity of the Baltic Sea ............................................ 135 4.3. Practical methods for tectonic earthquake identification ............................ 138 4.3.1. Spectral characteristics of earthquakes and explosions (Fourier spectra) .................................................................................... 140 4.3.2. Waves amplitudes ratio or spectra ratio P/S (P/Lg) .......................... 149 4.3.3. Time frequency analysis of earthquakes and explosions ................. 153 4.3.4. Complexity index as method of estimation of integral power ratio of S and P-waves ............................................................... 160 4.3.5. SOM method for discrimination between earthquakes and explosions .................................................................. 162 4.3.6. Nuclear Test Explosion Control in the context of seismic event type identification. An example of identification of nuclear explosion in the North Korea on September 3, 2017 by the BAVSEN network station ...................................................................... 165 5. Application of seismological methods in conditions of low seismicity ......... 176 5.1. Seismic zoning and microzoning .................................................................... 178 5.1.1. Main provisions of general seismic zoning ........................................ 179 5.1.2. Deterministic analysis of seismic hazard ............................................ 182 5.1.3. The probabilistic seismic hazard analysis ........................................... 184 5.1.4. Review of seismic zoning results in the East Baltic Region ............. 188 5.1.4.1. Seismic zoning of Belarus and the Baltic States ................ 188 5.1.4.2. Seismic zoning of Latvia – 1998 ........................................... 190 5.1.4.3. Seismic zoning of Latvia – 2007 ........................................... 193 5 5.1.4.4. GSHAP International Project ............................................... 201 5.1.4.5. Assessment of seismic hazard in the Baltic Region .......... 206 5.1.5. The basic concepts of seismic microzoning ......................................