Module 2 Seismic Hazards and Mitigation Measures PDF

HAZARDS, RISKS, VULNERABILITY CE305 – PRINCIPLES OF EARTHQUAKE ENGINEERING INTENDED LEARNING OUTCOMES DEFINE AND ENUMERATE SEISMIC HAZARDS IDENTIFY IMPACTS OF SEISMIC HAZARDS DIFFERENTIATE HAZARDS FROM RISK AND VULNERABILITY PRESENT VARIOUS EARTHQUAKE MITIGAT...

HAZARDS, RISKS, VULNERABILITY CE305 – PRINCIPLES OF EARTHQUAKE ENGINEERING INTENDED LEARNING OUTCOMES DEFINE AND ENUMERATE SEISMIC HAZARDS IDENTIFY IMPACTS OF SEISMIC HAZARDS DIFFERENTIATE HAZARDS FROM RISK AND VULNERABILITY PRESENT VARIOUS EARTHQUAKE MITIGATION STRATEGIES DESCRIBE POSSIBLE EARTHQUAKE SCENARIOS IN METRO MANILA PERFORM SELF-ASSESSMENT AT YOUR OWN HOME CE305 – PRINCIPLES OF EARTHQUAKE ENGINEERING SEISMIC HAZARDS AGENTS THAT CAUSE SIGNIFICANT DAMAGE TO THE BUILT ENVIRONMENT GROUND GROUND SHAKING INUNDATION FAILURE RELEASE OF HAZARDOUS LIQUEFACTION FIRE MATERIAL GROUND RUPTURE Earthquake movement along a fault which breaks the Earth's surface Underground services such as water, gas, electricity, internet, and sewer lines are at risk of damage, as well as road and rail networks. CE305 – PRINCIPLES OF EARTHQUAKE ENGINEERING GROUND SHAKING Trembling and shaking of the land that can cause buildings to vibrate Resonance is an increase in amplitude of a structure when its natural period closely resembles the period of ground motion Attenuation is the dissipation of the seismic waves as it propagates outward from the epicenter Amplification is the increase in amplitude of ground motion when seismic waves propagate through soft sedimentary soils CE305 – PRINCIPLES OF EARTHQUAKE ENGINEERING GROUND SHAKINGResonance (Demonstration) GROUND SHAKINGResonance (Demonstration) Every building has a natural period or frequency of vibration (taller buildings = longer period) The ground also has its own period or frequency (harder ground = lower period) CE305 – PRINCIPLES OF EARTHQUAKE ENGINEERING FIRE Initiate from gas or electrical sources which may ignite a flammable or combustible material. Earthquakes may also hamper movement of firefighters and access to water supplies Examples: 1923 Kanto Earthquake (70,000 deaths due to fire) 1994 Northridge Earthquake (shown on the right) LANDSLIDES Direct rupture and by sustained shaking of unstable slopes. Destroy buildings in their path, or block roads and railroad lines, or take hilltop homes with them as they tumble. They even can dam rivers on occasion FALL TOPPLE SLIDE SPREAD FLOW LANDSLIDES CE305 – PRINCIPLES OF EARTHQUAKE ENGINEERING TSUNAMI Sudden movement of the seafloor upward or downward during a submarine earthquake can generate very large sea waves, otherwise termed as tidal waves or tsunamis. LIQUEFACTION Water-saturated soil or sediment turns from solid to liquid as a result of rapid shaking during an earthquake. It usually happens for soils which are loose and sandy in nature. LIQUEFACTION LIQUEFACTION HAZARDS VS. VULNERABILITY VS. RISK When assessing dangers associated with earthquakes, there are 3 factors to consider: Hazard: Any phenomenon associated with an earthquake that may produce adverse effects on human activities Vulnerability: Conditions determined by physical, social, economic and environmental factors that increase susceptibility to hazards Risk: Expected losses to a community when a hazard event occurs A function of hazard and vulnerability Can be qualitative (high, medium, low) or quantitative (% losses or probabilities of damage) HAZARDS VS. VULNERABILITY VS. RISK HAZARD VULNERABILITY RISK TYPES OF VULNERABILITY Human vulnerability – relative lack of capacity of a person or community to anticipate, cope with, resist, and recover from the impact of a hazard Structural vulnerability – extent to which a structure or service is likely to be damaged or disrupted by a hazard event Community vulnerability – exist when the element at risk are in the path or area of the hazard and susceptible to damage CE305 – PRINCIPLES OF EARTHQUAKE ENGINEERING ELEMENTS AT RISK Community risk encompasses all potential losses from a hazard event. The elements at risk consist of a wide range of things that make up a society: People (life and health) Structures (buildings, roads, bridges) Infrastructures (water, electricity, communication, transportation) Economy (jobs, agricultural land, manufacturing) Services (schools, hospitals, religious institutions) Natural Environment (forest, beaches) CE305 – PRINCIPLES OF EARTHQUAKE ENGINEERING SEISMIC RISK ASSESSMENT QUANTITATIVE QUALITATIVE Expressed in terms of probabilities to Used when risk cannot be fully account for various scenarios expressed in absolute terms Considers different time-dependent May contain some numerical levels of ground motion / peak ground elements but can be summarized acceleration as high, medium, or low risk depending on the metric EARTHQUAKE MITIGATION Mitigation is the act of minimizing the risks posed by seismic hazards or reducing the vulnerability of elements likely affected by earthquakes. STRUCTURAL MITIGATION These are engineering-dependent mitigation activities with two types: REINFORCING PREVENTIVE Results in stronger structures that Primary function is to protect against are more resistant to hazards disaster EXAMPLES: EXAMPLES: Improving ductility of structural Base isolation and damper systems members Tsunami barriers Retrofitting Slope protection Pile foundations vs. liquefaction Structural design code compliance is very important!!! STRUCTURAL MITIGATION Retrofitting – structures are modified to enhance their seismic performance Why Retrofit? If structures are old and deteriorating Change in occupancy and/or loading Deficiencies in construction methods Advantages Can be cost-effective vs. building a new structure Better response against earthquakes CE305 – PRINCIPLES OF EARTHQUAKE ENGINEERING STRUCTURAL MITIGATION Retrofitting – structures are modified to enhance their seismic performance STRUCTURAL MITIGATION Concrete Jacketing External Post-Tensioning CE305 – PRINCIPLES OF EARTHQUAKE ENGINEERING STRUCTURAL MITIGATION Fiber-Reinforced Polymer Underpinning STRUCTURAL MITIGATION Base Isolation STRUCTURAL MITIGATION Buckling Restrained Brace STRUCTURAL MITIGATION Buckling Restrained Brace vs. Base Isolation vs. Conventional Structure STRUCTURAL MITIGATION Tuned Mass Damper STRUCTURAL MITIGATION Coastline Protection Seawalls Mangroves CE305 – PRINCIPLES OF EARTHQUAKE ENGINEERING STRUCTURAL MITIGATION Slope Protection Benching Gabion Walls Retaining Walls STRUCTURAL MITIGATION Slope Protection Coconet Vetiver Grass Drainage Shotcrete LOCATIONAL MITIGATION Physical planning approach which considers area of localized hazards Simply means avoiding the risk (with the help of hazard maps) Examples: Land use zoning Careful location of public sector facilities Reducing the concentration of essential elements at risk Prohibitions, or other measures to clear settlers from hazardous areas Making safer land available, or making alternative locations more attractive CE305 – PRINCIPLES OF EARTHQUAKE ENGINEERING LOCATIONAL MITIGATION OPERATIONAL MITIGATION Addresses the preparedness and resilience of people and society in general Promotes a “safety culture” – public awareness of hazards and continuous institutional and public effort to protect communities Examples: Public education and awareness Training for emergency Disaster preparedness and drills Community involvement in mitigation planning processes CE305 – PRINCIPLES OF EARTHQUAKE ENGINEERING OPERATIONAL MITIGATION OPERATIONAL MITIGATION OPERATIONAL MITIGATION OPERATIONAL MITIGATION OPERATIONAL MITIGATION ECONOMIC MITIGATION Economic activity is often diversified to reduce impacts of disasters to an industry. Examples Economic incentives and penalties (higher taxes for vulnerable structures) Grants and loans (upgrade assistance for repairs and retrofits) Risk Transfer (shares the risk with other involved parties, e.g. insurance) CE305 – PRINCIPLES OF EARTHQUAKE ENGINEERING EARTHQUAKE SCENARIOS IN MANILA CE305 – PRINCIPLES OF EARTHQUAKE ENGINEERING EARTHQUAKE SCENARIOS IN MANILA CE305 – PRINCIPLES OF EARTHQUAKE ENGINEERING EARTHQUAKE SCENARIOS IN MANILA CE305 – PRINCIPLES OF EARTHQUAKE ENGINEERING EARTHQUAKE SCENARIOS IN MANILA CE305 – PRINCIPLES OF EARTHQUAKE ENGINEERING EARTHQUAKE SCENARIOS IN MANILA CE305 – PRINCIPLES OF EARTHQUAKE ENGINEERING EARTHQUAKE SCENARIOS IN MANILA CE305 – PRINCIPLES OF EARTHQUAKE ENGINEERING EARTHQUAKE SCENARIOS IN MANILA CE305 – PRINCIPLES OF EARTHQUAKE ENGINEERING EARTHQUAKE SCENARIOS IN MANILA CE305 – PRINCIPLES OF EARTHQUAKE ENGINEERING HOW SAFE IS YOUR HOUSE? CE305 – PRINCIPLES OF EARTHQUAKE ENGINEERING HOW SAFE IS YOUR HOUSE? CE305 – PRINCIPLES OF EARTHQUAKE ENGINEERING KEY TAKEAWAYS Ground rupture, ground shaking, landslides, fires, liquefaction and tsunamis are the main seismic hazards Hazards are events which inflict damage. Vulnerability identifies the conditions of elements potentially affected by hazards Risk measures the likelihood and severity of impact of earthquakes Structural, locational, operational, and economic strategies are ways to mitigate seismic hazards Metro Manila can be severely damage by either a West Valley Fault or Manila Trench earthquake. Anyone can assess their own house condition with a simple checklist REFERENCES Anderson, G. (1997) Effect of Earthquakes. UCSD. https://topex.ucsd.edu/ es10/es10.1997/lectures/lecture20/secs.with.pics/node10.html CNN Philippines. (2019, April 23). A survival kit is an emergency must-have. ✓ Here are some items you should pack in case disaster strikes [Facebook Update]. https://www.easybib.com/guides/citation-guides/apa-format/how-to-cite-facebook-status-update-apa/ FM Global. (2015). Understanding the Hazard – Fire Following the Earthquake. FM Insurance Company Limited. Gonzales, G. (2021). Google launches Android Earthquake Alerts System in the Philippines. Rappler. https://www.rappler.com/technology/innovations/google-android-earthquake-alerts-philippines IRIS. (2020). Building Resonance: Structural Stability During Earthquakes. https://www.iris.edu/hq/inclass/animation/building_resonance_the_resonant_frequency_of_different_seismic_waves Kageyama, Y. and Yamaguchi, M. (2021). Powerful Japan quake sets off landslide, minor injuries. https://phys.org/news/2021-02-strong-earthquake-japan-northeastern-coast.html NDRRMC. (2015). Metro Manila Earthquake Contingency Plan. NIDM. (2019). Training Programme on Child Centric Disaster Risk Reduction PHIVOLCS. (2018). Introduction to Landslides. https://www.phivolcs.dost.gov.ph/ index.php/landslide/introduction-to-landslide PHIVOLCS. (2018). Landslide Preparedness. https://www.phivolcs.dost.gov.ph/ index.php/landslide/introduction-to-landslide Oreta, A. (2017). Earthquake Risk Reduction. De La Salle University CIV525M. RWTN Aachen University. (2016). Soil Liquefaction. https://www.youtube.com/watch?v=ZMWKTuRgJjY Solidum, R. (2019). Earthquake Scenarios for Greater Metro Manila Area. PHIVOLCS.