Geology PDF

MODULE 1 GEOLOGY Geology WHY WE STUDY GEOLOGY IN CIVIL is...

MODULE 1 GEOLOGY Geology WHY WE STUDY GEOLOGY IN CIVIL is the science that deals ENGINEERING with the study Earth. physical and chemical changes (SPECIFICALLY IN that occur on its surface and in EARTHQUAKE its interior. history of the planet and its life ENGINEERING?) forms. Modern geology significantly Engineering geology overlaps all other earth sciences, d e a l s w i t h t h e s t u dy o f including hydrology and the the structure of the atmospheric sciences, and so is e a r t h i n re l a t i o n to t h e treated as one major aspect of integrated earth system science civil engineering for and planetary science. the execution of safe Plays a major roles in different and cost-effective engineering disciplines including d e s i g n f or con s t r u c t i o n Civil Engineering and projects. Earthquake Engineering. What can be the benefits of What can be the benefits of Geology in construction? Geology in construction? 1. Geology is an "environmental 3. The knowledge about the nature of science:" it is essential for the rocks is very necessary for u n d e r s t a n d i n g e a r t h p ro ce s s e s , a n d tunnelling, constructing roads, dams, important to understanding both bridges and buildings where they are natural and anthropogenic to be built. catastrophes. 4. Geology helps to identify area 2. Geology provides knowledge about susceptible to failures due to the site used in the construction of geological hazards such as earthquake, buildings, dams, tunnels, tanks, landslides, weathering effects, etc. reservoirs, highways and bridges.  Physical Geology / Branches of Geology Geomorphology This is a ls o va rio u s ly d e s c r i b e d a s Physical Geology / Geomorphology dynamic geology or Geomorphology. Mineralogy It deals with: Petrology I) Different physical features of the earth, Historical Geology such as mountains, valleys, rivers, lakes Economic Geology glaciers and volcanoes in terms of their origin and development. II) The different changes occurring on the earth surface like formation or disappearance of rivers, springs and lakes. Physical Geology / Mineralogy Geomorphology This deals with the study of minerals. Minerals are basic units with different It deals with: rocks and ores of the earth are made up III) Geological work of wind, rivers, oceans, of. and groundwater and their role in constantly moulding the earth surface features. Petrology IV) Natural phenomena like landslides, earthquakes and weathering. It deals with the mode of formation, structure, texture, composition, occurrence, and types of rocks. Internal Structure of the Earth Historical Geology Crust The climatic and geological changes including tectonic events in the Is the uppermost solid shell of geological past can also be known from the earth which makes up less than 1 percent of Earth these investigations. by mass, consisting of oceanic crust and continental crust Economic Geology w i t h va r y i n g t h i c k n e s s i n different area as follows: Under the oceans : Minerals can be grouped as general rock 5-6km forming minerals and economic minerals. Under the continents: 30- 35km  Internal Structure of the Earth Internal Structure of the Earth Crust Mantle The tectonic plates are always Is the zone within the earth slowly moving, but they get that lies between Earth’s stuck at their edges due to core a n d t h e outer m o s t friction. layer. When the stress on the edge I t i s h o t a n d re p re s e n t s overcomes the friction, there is about 68 percent of Earth’s an earthquake that releases mass. energy in waves that travel through the earth's crust and cause the shaking that we feel. Internal Structure of the Earth Mantle Mantle Based on studies, mantle is made of rock based B e l ow t h e c r u s t l i e s t h e on evidence from seismic waves, heat flow, and dense mantle, extending to a meteorites. Scientist know that the mantle is depth of 2890 km. It consists extremely hot because of the heat flowing of dense silicate rocks. outward from it and because of its physical properties. Heat flows in two different ways B o t h P - w ave s ( p r e s s u r e within the Earth: conduction and convection. waves) and S-waves (shear waves) from earthquakes travel through the mantle, demonstrating that it is solid. Mantle Mantle Conduction Convection I s defined as the heat transfer that occurs is the process of a material that can move and flow may through rapid collision of atoms, which can only develop convection currents. Convection in the mantle is the happen if the material is solid. same as convection in a pot of water on a stove. Heat flows from warmer to cooler places until all are the same temperature. The mantle is hot mostly because of heat conducted from the core.  Internal Structure of the Earth Plate Tectonics Core The plates are made up of the lithosphere (is the solid, outer part of Earth, includes the I t is the very hot and dense brittle upper portion of the mantle and the center of the planet. crust). During the 1950s and early 1960s, scientists set up seismograph networks to see I t is mostly iron me ta l a n d if enemy nations were testing atomic bombs. makes up about 31 percent of These seismographs also recorded all of the the Earth’s mass. earthquakes around the planet. The seismic records could be used to locate an earthquake’s The deepest earthquakes epicenter, the point on Earth’s surface directly occur within the core of above the place where the earthquake occurs. subducting slabs - oceanic Earthquake epicenters outlines these tectonic plates that descend into the plates. Mid-ocean ridges, trenches, and large Earth's mantle from faults mark the edges of these plates along convergent plate boundaries. with where earthquakes occurs. Plate Tectonics The lithosphere is divided into a number of smaller parts How Plate Tectonics Move called “tectonic plates”. Tectonic plates move and interact with one another, driven by convectional forces within the Earth. The movements and interactions of these plates produces earthquakes, volcanoes, mountain ranges, ocean trenches and other geological processes and features. Plate Tectonic Boundary Plate Tectonic Boundary Most seismic activity occurs at D i v e r g e n t three types of Boundary plate boundaries: i s a l i n e a r D i v e r g e n t feature that Boundary exists between Co nve rg e n t two tectonic Boundary plates that are T r a n s f o r m moving away Boundary from each other. Plate Tectonic Boundary Plate Tectonic Boundary C o n v e r g e n t Boundary T r a n s f o r m Boundary Convergent plate boundaries are A t r a n s f o r m locations where boundary occurs lithospheric plates when two tectonic are moving towards plates move past o n e a n o t h e r. T h e o n e a n o t h e r. S h e a r plate collisions that stress operates at occur in these areas t r a n s f o r m c a n p r o d u c e earthquakes, volcanic boundaries, which a c t i v i t y, a n d c r u s t a l involves sliding deformation. motion. END  MODULE 2 EARTHQUAKE Earthquake Engineering Earthquake Engineering Can be defined a s the branch of Scope: engineering devoted to mitigating Seismicity, Nature, M e a s u r e s , a n d earthquake hazards, in this R e c o r d i n g o f broad sense, earthquake Earthquakes engineering covers the P l a n n i n g for S e i s m i c Risk Assessment and Mitigation investigation and solution of the Analysis, Design, and problems creat e d by d a m a g i n g C o n s t r u c t i o n o f earthquakes, and consequently Earthquake Resistant the work involved in the practical Structures Evaluation of Buildings for application of these solutions, i.e. Earthquake Resistance in planning, designing, Retrofitting of Earthquake constructing, and managing damaged Structures Earthquake Management earthquake-resistant structures and Security and facilities.  Earthquakes Earthquakes Every year, more than 3 million Is the motion or vibration, earthquakes take place, most of these unnoticed by humans. In sometimes violent, of the contrast, a severe earthquake is the earth’s surface that follows a most frightening and catastrophic event of nature which can occur release of energy in the earth’s anywhere on the surface of the planet. crust. This energy can be Although usually lasting only generated by a sudden seconds, a severe earthquake in a densely populated area may have dislocation of segments of the catastrophic effects causing the crust by a volcanic eruption or death of hundreds of thousands of people injuries, destruction, and even by a man-made enormous damage to economies of the affected area. explosions. Earthquakes Sources of Ground Movements Besides the immediate, obvious Tectonic Earthquakes threat presented by an earthquake, Volcanoes it can also set off several other Explosions natural hazards. The energy release Collapse of Mines and resulting from earthquakes can Large Reservoirs easily trigger slope failure. A t s u n a m i m ay b e f o r m e d w h i c h causes flood on coastal areas. These events occur along with volcanic activity, resulting in even more potential danger.  Earthquake: Fault Lines Earthquake: Fault Lines Normal Fault Faults are cracks in Normal faults cracks the lithosphere where one mass of caused by the rock slides downward and pulls away from stresses created as another mass of rock. sections of a plate As these plates are are moving in slowly splitting apart different direction. and pulling away from In this c as e , t h e each other, the normal faults are formed this earthquake event is way. called a slip. There Normal faults are are number of associated with different types of downward movement faults, but most can on a sloping fault as the two plates move be divided into apart. three categories: Deep sea ridges in strike-slip faults, the Atlantic and normal faults, and Pacific are where reverse faults the largest normal faults are formed along these ridges. An example of a normal fault is the infamous San Andreas Fault in California. Earthquake: Fault Lines Reverse Fault Also known as thrust faults, which happens w h e n p l a t e s a re being pushed t o g e t h e r. T h i s involves upward movement as the plates collide and buckle upwards. This kind of event signifies a compression of the Earth’s c r u s t. These are usually caused by plates pulling apart and colliding with continental plates. An example of a reverse fault is the Rocky Mountains, Himalayas. Earthquake: Fault Lines Strike-slip Fault A strike-slip fault occurs in an area where two plates are sliding past e a c h o t h e r. I n re l a t i o n t o t h e ground surface, the slip involves s i d e w a y s m o v e m e n t. Strike-slip faults are found in California, the San Andreas fault being the most famous which has caused many powerful earthquakes. An example of a Strike-slip fault are the Anatolian Fault in Turkey and the Alpine Fault Earthquakes: Seismic Waves in New Zealand The epicenter of an earthquake sends out waves which are like an object dropped on to a still body of water that sends out ripples. After the stone hits the water ripples move outwards from the center in every direction. An earthquake releases energy as shock waves, the so-called seismic waves, which ripple across the Earth’s surface. The seismic waves created as they move from the epicenter an earthquake vary and can travel up to 2 miles per seconds. There are two types of seismic waves: Body Waves, which consists of P and S waves, and Surface Waves, which consists of Love and Rayleigh Waves.  SEISMOLOGY Seismology is the study of earthquakes and seismic waves that move through and around the earth. A seismologist is a scientist who studies earthquakes and seismic waves. https://www.youtube.com/watch?v=IENdh3TZHD4 Earthquake Focus Earthquake Strength: Intensity The oldest useful yardstick of the strength of a n The focus of an earthquake is where earthquake is the earthquake intensity. pressure builds along a faults line which fails deep underneath the crust of the The intensity of an earthquake is used to determine its Earth. The point directly above the severity at a particular location as determined by human reactions to Earth’s movement, observed damage to focus is termed the epicenter. structures, and observation of other physical effects. Earthquake foci are confined to within Because earthquake intensity assessments do not depend a limited zone of the upper Earth, the on instruments, but on the actual observation of effects in lower boundary occurring at around the seismal zone, intensities can be assigned to historical 700 km depth from the surface. No earthquakes. In this way the historical record becomes of earthquakes are known to have utmost importance in modern estimates of seismological originated below this level. risk.  Earthquake Strength: Intensity Earthquake Strength: Magnitude Because intensity scales are subjective and highly If sizes of earthquakes are dependent on the construction practices and socio-economic conditions of a country, and bear to be compared worldwide, no specific relation to the ground motion, a measure is needed that correlation among the various intensity scales is does not depend, as does not easily done. intensity, on the density of population and type of These intensity scales are based on three construction. A strictly features of shaking: ü perception by people and animals; quantitative scale that can ü performance of buildings; be applied to earthquakes ü changes to natural surroundings. Earthquake Strength The strengths of earthquakes may PHILVOLCS Earthquake be expressed in Intensity Scale terms of intensity (PEIS) or magnitude. END  EFFECTS OF MODULE 3 EARTHQUAKE Effects of Earthquakes Comprehensive regional earthquake impact a sse ssm e n t requires an interdisciplinary framework that e n c o m p a s s e s t h e d e f i n i t i o n of t h e Damage to Buildings and Lifelines hazard event, physical damage and social a n d economic consequences. Such an integrated framework may Extensive structural damage is suffered by buildings, bridges, provide the most credible estimates with associated uncertainty that can highways and other lifelines during earthquakes. Seismic stand scientific and political scrutiny. Physical damage should be evaluated vulnerability of s t r u c t u re s v a r i e s a s a function of for t h e b u i l d i n g s t o c k s , l i f e l i n e construction materials and earthquake action‐resisting systems, transportation networks and critical facilities. Short‐ and system employed. long‐term effects should be considered in quantifying social and economic consequences. Damage to Buildings and Lifelines Lifelines are those services that are vital to the health and safety of communities and the functioning of urban and industrial regions. These include electric power, gas, water and wastewater systems. Infrastructures, such a s transportation systems (highways and railways), bridges, ports and airports are also classified as lifelines. EFFECTS ON THE GROUND A n a l y s i s of e a r t h q u a k e ‐ i n d u c e d d a m a g e i n d i c a t e s t h a t g ro u n d effects are a serious contributor to damage of the built environment. Local geology and topography influence the travel path and amplification characteristics of seismic waves. EFFECTS ON THE GROUND EFFECTS ON THE GROUND Settlement and Uplift Surface Rupture Fault ruptures may cause large vertical movements of the ground. These movements Rupture of the ground surface may be in turn cause severe damage to the foundations of buildings, bridge footings and to induced by intense and long shaking underground networks. The collapse of several approach structures and abutments of as well as fault ruptures. These may bridges was observed in some previous earthquakes. Settlement, tilting and sinking of generate deep cracks and large gaps buildings have been observed in the aftermath of several earthquakes worldwide. (ranging in size from a few metres to several kilometres). EFFECTS ON THE GROUND EFFECTS ON THE GROUND Liquefaction Landslides Excessive build‐up of pore water pressure during earthquakes may lead Landslides include several types to the loss of stiffness and strength of soils. of ground failure and movement, such as rockfalls, deep failure of slopes and shallow debris flows. These failures are generated by the loss of shear strength in the soil.  Human and Financial Losses During the twentieth century over 1200 destructive earthquakes occurred worldwide and caused damage estimated at more than $1 trillion (Coburn and Spence, END 2002). If these costs are averaged over the century, annual losses are about $10 billion. Monetary losses due to collapsed buildings and lifeline damage are s u b s t a n t i a l. One of t h e m o s t severe consequences of earthquakes is the cost of recovery and reconstruction.