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Principles of the Seismology and Seismic Engineering

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Principles of the Seismology and Seismic Engineering Principles of the Seismology and Seismic Engineering Assoc. Prof. RNDr. Dana Prochazkova, PhD., DrSc. Czech Technical University in Praha CONTENT Introduction Earthquake causes Earthquake characteristics Earthquake impacts and their consequences Seismic regime Seismological characteristic of Europe Seismic vulnerability, mitigation, prevention and response Principles of seismic protection in national standards, EU civil protection directives and the IAEA standards Earthquake - is a physical phenomena that is a consequence of processes that lead to accumulation of energy in limited space in the Earth interior and to its sudden release if energy size exceeds physical material limits (stress limit, phase transition limit), - is observed as vibrations of the Earth's surface of a different intensity, - causes harms and losses on human assets, i.e. human lives and health, property, infrastructures and environment. Greek philosopher Aristotle classified earthquake into 6 categories according to observed Earth ´s surface movements. Chinese scientist Chan Chen constructed instrument for earthquake registration in 132 AD. Seismology – science dealing with earthquakes Seismic engineering – the discipline the aim of which is to construct infrastructures and buildings resistant to earthquake and similar phenomena impacts and by this way to protect human lives and health and human property. Seismicity – general term. Instrumental seismology – half of 19th century. 1897 – mathematical theory of the P (longitudinal – primary), S (transversal – secondary) a L (surface) waves Physical models of earthquake – rheology. Earthquakes – enable the Earth's interior research (Earth's crust, mantle, external core, internal core and its parts). Bucharest - March 4, 1977 Spitak - December 7, 1988 Dolní Žandov - December 21, 1985 Petrochemie in Izmit – August 17, 1999 Petrochemie in Izmit – August 17, 1999 Petrochemie in Izmit – August 17, 1999 Japan – March 11, 2011 Japan – March 11, 2011 Zaplavené letiště v Sendai Japan – March 11, 2011 – Sendai airport Japan – March 11, 2011 - Fukushima NPP Tsunami se blíží k JE Fukushima JE po průchodu tsunami After earthquake After tsunami Recorded seismic events: • natural earthquakes, • induced earthquakes – man-made, induced by human activities • artificial explosions, • vibrations of natural or artificial origin – consequences of technological processes and natural phenomena as fall of meteorites, aircrafts, bombs etc. Tsunami - waves on sea induced by earthquake the focus of which is under the sea bottom. Mikroseisms – permanent Earth's surface vibration. Faults – foci of natural earthquakes in Earth's Crust and Upper Mantle Strike slip Thrust Normal Natural earthquakes are of: • tectonic origin (90%), • volcanic origin (7%), • collapse of underground spaces (3%) The most harms and losses on human assets are caused by tectonic earthquakes. Earthquake epicentres in last 800 years Microearthquakes 1980 - 2000 Induced (man-made) earthquakes – artificially triggered seismicity • cause - the perturbation of the underground mechanical equilibrium, due to industrial activities (mining, dams, geothermal, hydrocarbon reservoirs), induce deformation of involved sites, • located in different tectonic settings, • types: * reservoir - induced seismicity - e.g. Lake Kremasta in Greece 1966, * rockbursts – mining – rockfalls, shaking, bumps, outbursts (methane release), * seismicity triggered by injection of fluids into rocks - special technology of mining, * seismicity triggered by withdrawn of fluids from surface formations – special technology of mining, * earthquakes stimulated by seismic vibration signals - special technology of mining, * stimulated by artificial explosions (mining regions, test sites). Earthquake foci – mostly on lithosphere plates boundaries Daily is recorded ca 8000 earthquakes with magnitude 2 or lower Annually is recorded: • ca 7000 – 9000 medium earthquakes with magnitude 4 and higher, • ca 18 – 20 strong earthquakes with magnitude 6 – 7, • at least 1 very strong earthquake with magnitude 8 and higher Earthquake Mw Mo (dyne-cm) 1960 Chile 9.6 2.5 x 1030 1964 Alaska 9.2 7.5 x 1029 1906 San Francisco 7.9 9.3 x 1927 1971 San Fernando 6.6 1.0 x 1026 1976 Tangshan 7.5 1.8 x 1027 1989 Loma Prieta 6.9 2.7 x 1026 1992 Cape Medocino 7.0 4.2 x 1026 1994 Northridge 6.7 1.3 x 1026 1995 Kobe 6.9 2.5 x 1026 2004 Indonesia 8.4 1.3 x 1028 2010 Haiti 8.0 2.5 x 1027 2011 Japan 9.0 2.5 x 1029 E- epicentre – projection Of H to Earth's surface H – hypocentre – point representation of focus h – focal depth Earthquake parameters Focus = focal domain • geographic co-ordinates of epicentre E Earthquake size is measured by: • focal depth h • Intensity (I), • size • Energy (ET), • Seismic energy (E) • Magnitude (M) – Richter scale Earthquakes are • Ground acceleration (a), * Shallow – h 50 km • Ground velocity (v), * Intermediate - 50 ‹ h 450 km • ZemětřeseníGround displacement podle h(d), jsou:mělká ( méně* Depth než 50- 4 50km ‹), h ca750 km • středněSeismic hluboká moment (M (50o) – 400 km), hluboká ( 400 – 750 km ) • Stress drop (σ) Total energy release at earthquake at time interval dt - dW dW = mechanical energy (performed work – deformation + kinetic energy) + heat energy Seísmic energy – part of kinetic energy E = ∫ ∫ ε dS dt, 0 S - c En = Eo exp (- d Dn) Dn . Dependence of seismic energy on magnitude: log E = 11.3 + 1.8 M I A- seismic wave attenuation: log a = ---- - 0.5 3 Intensity attenuation Kövestligethy formula: Io - In = 3 log (Dn / h) + 3 log e (Dn – h) α Blake formula: Io - In = k log (Dn / h) Bohemian Massif: log E = 12.40 + 1.13 Io Gutenberg-Richter: log E = 11.3 + 1.8 M Seismograph – instrument for recording the earthquakes (if ground acceleration is measured – accelerograph) Seismogram – earthquake record (in case of ground acceleration recording – the accelerogram) Magnitude – C. F. Richter 1935 M = log (A/T)max + (, h) A – amplitude, T – period, - correction function (depends on wave type), - epicentral distance, h – focal depth) S ZP O P granit Intensity - scales: g C MCS, MSK-64, MM – 12 degree P* JMA – 7 degree bazalt M P n Travel time curve - f (, h) - dependence of time spreading the real wave on epicentral (hypocentral) distance – it depends on wave type - t ( r ) = T - H ; time in site, time in focus. Isoseismal map - scenario of earthquake impacts Typical isoseismals – isoseismal form depends on focal region and on focal depth. Empirical relations derived for Europe, M = 4.5 – 7.4, shallow earthquakes: log Mo = (9.95 0.24)+(1.40 0.14) M log = - (3.15 0.24)-(0.29 0.09) R + (1.01 0.08) M log = - (20.96 0.53)-(0.13 0.05) R + (1.26 0.18)log Mo log u = - (2.60 0.11)-(0.39 0.09) R + (0.63 0.02) M R- focal dimension, u – fault displacement [Mo] = N m, [R] = km, [ ] = MPa, [u] = mm Vrancea intermediate earthquakes: log Mo = (8.98 0.80) + (1.5 0.12) M PHYSICS: Mo = μ AZ u μ – torsion modulus, AZ – active fault plane, u – fault displacement EARTHQUAKE IS completely DESCRIBED BY 2 PARAMETERS – e.g. M and or Mo and !!!!!! Relation among the focal parameters Mw – Kawasaki / moment magnitude – derived from seismic moment (greater than M calculated from seismic waves) Seismogram: P vlny – 6 km/s; S vlny – 3.3 km/s; L vlny – 3 km/s Length of time interval between P and S inputs depends on epicentral distance and recording place. With increase of epicentral distance the seismogram complexity increase as a consequence of recording the reflected, surface and other wave types. There are earthquakes the records of which do not respect present standards on earthquake record Spectrum of acceleration in near zone – different from distant zone (red zone – strong dependence on local geological structure) Differences in focal mechanisms (documented by amplitude rate S to P changes) of near earthquakes Fault structure in Western Bohemia – causes of different earthquake mechanisms Reaction of buildings to seismic waves Human lives, health and security EXTREME DISASTER Property Welfare SECONDARY Environment IMPACTS caused by cascade Energy failures of infrastructures Water DIRECT IMPACTS Sewage Transport Protection measures Infrastructures Cyber and activities are prepared Finance only for impacts denoted Emergency by bold arrow Products Governance Nuclear Technologies Chemical Bio Accelerograms Response spectra – RG 1.60 (US NRC) Response spectra Response spectrum - Atomenergoproject Real response spectra Intensity attenuation with distance – usually azimuthal variations are observed in each focal region 10 100 log r 0.1 1 It corresponds to focal 10 zone dimension log E / E 0 Energy attenuation with distance Acceleration attenuation with distance – strong regional The earthquake foci mostly concentrate to regions that we called “focal provinces – zones, regions”. The boundary of focal provinces are defined as a boundary that surrounds: • all known earthquake foci occurring in the historical time and in the case when there are the reliable evidence on pre- historical foci from the research of paleoseismicity, so the boundary also includes those, • the region in which the earthquakes with the same characteristics of seismic regime occur, • the region with the same geological, tectonic and recent movements characteristics. Map of focal regions and regions with diffuse seismicity Findings from research of earthquakes : 1. From earthquake foci space distribution it follows that earthquake foci are mostly connected with faults. 2. In recent period only certain parts of faults are seismoactive, namely
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