1.3

• How many deaths are caused by earthquakes annually?

  Approximately 10,000 deaths occur annually from earthquakes.
• Where do most earthquakes occur?

  95% of earthquakes occur along plate boundaries.
• What happens during an earthquake in terms of pressure release?

  Friction between tectonic plates causes pressure to build, which is released when rocks fracture along faults. The energy released as seismic waves causes the earthquake.
• What is the focus (hypocenter) of an earthquake?

  The focus (hypocenter) is the point within the Earth where pressure is released, causing the earthquake.
• What is the epicenter of an earthquake?

  The epicenter is the point on the Earth’s surface directly above the focus, where the most damage occurs.
• What are the three main types of seismic waves?

  P waves (Primary waves): Fastest, travel through solids and liquids, least damaging.S waves (Secondary waves): Slower, only travel through solids, more damaging. L waves (Love waves): Slowest, most damaging, shake the ground from side to side.
• How is the magnitude of an earthquake measured?

  Earthquake magnitude is measured by the Moment Magnitude Scale (MMS), which evaluates the energy released at the epicenter using data on seismic waves, rock movement, and fault surface.
• What is the Moment Magnitude Scale (MMS)?

  The Moment Magnitude Scale measures the energy released by an earthquake, ranging from 1 to infinity. The largest recorded earthquake was a 9.5 magnitude in Chile (1960).
• How is earthquake intensity measured?

  Earthquake intensity is measured by the Modified Mercalli Intensity Scale (MMIS), which assesses the impact on people, structures, and the environment. The scale ranges from I to XII.
• What are primary impacts of earthquakes?

  Primary impacts are direct results of the earthquake, such as crustal fracturing and immediate destruction.
• What are secondary impacts of earthquakes?

  Secondary impacts are indirect effects of the earthquake, such as landslides, avalanches, tsunamis, and liquefaction.
• When did the Loma Prieta earthquake occur, and what was its magnitude?

  The Loma Prieta earthquake occurred on October 17, 1989, with a magnitude of 6.9 near San Francisco.
• What were some social impacts of the Loma Prieta earthquake?

  12,000 homes were damaged. 40 buildings collapsed in Santa Cruz. Many schools were closed, disrupting education. Approximately 2,600 businesses were damaged, causing closures and job losses
• What were some economic impacts of the Loma Prieta earthquake?

  $1.8 billion in damage to transportation systems, including the collapse of part of the San Francisco–Oakland Bay Bridge. Economic downturn due to the destruction of commercial hubs. Decreased tourism to the Bay Area, affecting revenue.
• What were the environmental impacts of the Loma Prieta earthquake?

  The Marina District was severely affected due to liquefaction of soft sandy soils. The Cypress Freeway collapsed, causing 42 of 67 earthquake-related deaths. Triggered multiple fires and hazardous material leaks, including ruptured gas lines in the Marina District.
• What are aftershocks?

  Aftershocks are smaller earthquakes that occur after a major earthquake as the Earth readjusts along the fault line. They can cause additional damage and hamper rescue efforts.
• How can the size of an initial earthquake affect aftershocks?

  The larger the initial earthquake, the more numerous and larger the aftershocks. They can cause additional damage and loss of life, as seen in the Christchurch, NZ aftershock in 2011
• What are intra-plate earthquakes?

  Intra-plate earthquakes occur within the middle of tectonic plates, far from plate boundaries. Their cause is uncertain but is likely due to stresses from ancient faults becoming active again.
• How are earthquakes predicted?

  Earthquakes are generally hard to predict. However, places with a history of large earthquakes are likely to experience another. Forecasting is more general, such as the 67% chance of a "serious" earthquake in San Francisco by 2040.
• What are some earthquake "precursors"?

  Researchers focus on precursors like foreshocks (smaller shocks before the main earthquake), but none have proven to be reliable in predicting major earthquakes.