Earthquakes Flashcards

Question

Define seismometer

Answer 1

The part of the seismograph that detects the movement

Answer 2

A scientist who uses data from seismographs and seismometers to study earthquakes and seismic waves

Answer 3

**Seismic Hazard Assessment** Historical data: Analysing the historical records of earthquakes in a region to identify patterns and recurrence intervals of seismic activity Seismic gaps: Identifying areas along known fault lines that have not experienced recent earthquakes (seismic gaps) and are therefore considered potential sites for earthquakes Paleoseismology: Studying geological evidence of past earthquakes (eg. trenching studies along faults) to extend the historical record and understand long term seismic behaviour **Seismic Monitoring Networks** Seismometer Networks: Deploying dense networks of seismometers to continuously monitor ground vibrations. They help detect foreshocks. GPS and InSAR: To measure ground deformation. Slow movements or strain accumulation can indicate increasing stress along faults **Statistical and Probabilistic Models** Probabilistic Seismic Hazard Assessment: Combing historical earthquake data, geological information and statistical models to estimate the probability of different levels of seismic shaking occurring in a region of a specific period. Earthquake Forecasting: Developing short term and long term forecasts based on statistical patterns of earthquake occurrences. They provide probabilities but do not predict specific events **Early Warning Systems** Earthquake Early Warning (EEW): Networks of seismic sensors used to detect the inital, less damaging P-waves (primary waves) of earthquake. Early warning can be issued before more destructive S-waves (secondary waves) and surface waves by - * Automatic Alerts - Systems that automatically send alerts to public via mobile phones, radio, TV etc. * Automated Safety Measures - Early warnings can trigger automated responses eg. shutting down gas lines, stopping trains and opening fire station doors. **Geophysical and Geochemical Monitoring** Groundwater changes: Changes in groundwater levels and chemistry can sometimes precede earthquake due to stress changes in earth's crust Radon emissions: Measuring radon gas emissions from the ground, as increased emissions sometimes happen before earthquakes

Answer 4

**Building design and construction** Seismic resistant structures: By using flexible materials, reinforced concrete and steel frames to absorb and dissipate energy Base Isolation systems: Allow building to move independently of its foundations reducing shaking of structure Retrofitting: Retrofit buildings (especially older ones) by adding bracing, reinforcing walls and improving foundations to better resist seismic forces **Urban planning and land use** Zoning regulations: Enforce zoning laws that prevent contruction on fault lines, unstable slopes, or areas prone to liquefaction Land use planning: Develop open space, parks and wide roads that can serve as emergency evacuation routes and gathering points during earthquakes. Lifeline infrastructure: Design critical infrastructure (hospitals, fire stations, bridges, utilities) to be earthquake resistant and ensure they are not all clustered in same high risk area **Early Warning Systems** Seismic sensors: Deploy network of seismic sensors to detect inital tremors and provide early warning before main shaking so people can take cover. Automated systems to shut down critical infrastructure Public Alerts: Use mobile alerts, sirens etc to warn public quickly **Community Education and Preparation** Public awareness campaigns: Educate public about earthquake risks, safe practices during earthquake and the importance of preparation Drills and training: Conduct regular earthquake drills in schools, workplaces and communities Emergency kits: Encourage people to prepare emergency kits with essential supplies like water, food, medications and first aid materials **Emergency Response Planning** Disaster response plans: Develop comprehensive emergency response plans that outline roles and responsibilities for government agencies, emergency services and community organisations. Coordination: Ensure effective communication and coordination among local, regional and national emergency services and agencies Resilient infrastructure: Design resilient buildings and areas than can serve and shelters and command centres during earthquake

Answer 5

P waves, S waves and surface waves

Answer 6

Tiltmeters, lasers etc.

Answer 7

Slow tilting of land and foreshocks

Answer 8

1. **Damage to Infrastructure** * Seismic waves cause buildings and bridges to sway and collapse * Falling debris from collapsing infrastructure can crush/suffocate people causing death * Rescue workers must then search through rubble to find survivors and recover bodies * Causes economic losses Example: 1994 Northridge Earthquake, California, USA -6.7M -Several freeway overpasses collapsed -Thousands of buildings in Los Angeles area damaged 2. **Loss of Life** * Due to collapsing structures, falling debris, etc. * The instensity of an earthquake and level of preparedness incluences number of casualties Example: 2010 Haiti Earthquake -7.0M -160,000 people killed - one of the deadliest earthquakes in the 21st century 3. **Tsunami** * Occur due to earthquakes at sea * Subducting plate can cause overlying plate to be forced suddenly upwards * This upward movement creates excess hump of water on ocean surface * This hump collapses and spreads all directions, travelling at up to 970km/h * As tsunami gets to coastline, the bottom of the wave comes in to contact with the shore and slows down due to friction, causing the rest of the wave to stand upwards and crash into the coastline at speed Example: 2004 Indian Ocean Earthquake - 9.1-9.3M - Massive tsunami affecting countries across Indian Ocean - 230,000 deaths and devastation along coastlines **Liquefaction** * During earthquake, the ground shaking forces groundwater upwards and saturates the soil * In certain soil types, the soil can take on the properties of a liquid * Soil affected by liquefaction is unable to support buildings, causing them to collapse * Can also cause gas and sewage pipelines to sink and break leading to fires or contamination of water supplies Example: 1923 Great Kanto Earthquake, Japan - Tokyo and Yokohama experienced liquefaction causing buildings to sink

Answer 9

**Magnitude** * Magnitude or an earthquake refers to the amount of energy it releases * Larger magnitude earthquakes cause more damage * M5-M7= moderate * M7+ = major **Depth of Focus** * Refers to where earthquake occurs beneath surface * Shallow focus = more damage as shaking close to surface **Rock Type** * Some rocks have natural cracks/joints eg. sedimentary * They can fracture easier **Time of Day** * Earthquakes at rush hour can affect a lot of people * Earthquake at night means people are asleep to have slower reactions **Location** * High population density areas - more people affected Eg: 39m people line in California, 4m live along San Andreas Fault * Low population density = less people affected Eg: Alaska 1960 - largest every earthquake recorded 760,000 population, 100 deaths **HIC vs LIC** -High Income Country Eg: Japan, New Zealand * Wealthy * Very good infrastructure * Very good response plans * Building regulations * Less people die due to this -Low Income Country Eg: Nepal, Pakistan * Less money for infrastructure * More people die due to this

Earthquakes Flashcards

(35 cards)