Earthquakes Flashcards
(34 cards)
what is the focus/hypocentre?
the spot under the surface of the ground where the earthquake happens
what is the epicentre?
the spot on the surface directly above the focus
what are P waves?
these are the fastest waves and reach the surface first, they are high frequency and travel through the mantle and core to opposite sides of the earth, they travel at between 4 and 7km/second
what are S waves?
these are half as fast as P waves and are second to reach the surface, they are high intensity waves that shake side to side through the crust and mantle only, they travel at between 2 and 5km/second
what are Love waves?
these are the slowest waves and cause the most damage, they are surface waves and travel between 2 and 3km/second
what are Rayleigh waves?
these radiate out from the epicentre in low frequency, rolling motions, these travel between 2 and 3km/second
what is the Richter scale?
it was developed in the 1930s and it uses a logarithm to mathematically determine the magnitude of earthquakes, each increase in the scale is 30 times more
what is the Movement Magnitude Scale?
developed in the 1970s, it is more effective for large earthquakes
what is the Modified Mercalli Scale?
it measures the intensity of the earthquake event and its impacts
how can earthquakes cause landslides?
earthquakes cause loose rocks and soil on slopes to move, often these landslides can cause more destruction and loss of life than the initial quake
how can earthquakes cause mudflows?
in areas where the water content of the soil is high, an earthquake can trigger a mudflow where the mixture of mud and water slides downhill
how can earthquakes cause tsunamis?
they are caused by ocean floor earthquakes, submarine volcanic eruptions and landslides
what are the possible signs of an earthquake?
- microquakes before the main tremor
- bulging of the ground
- decreasing radon gas concentrations in groundwater
- raised groundwater levels
- electrical and magnetic changes within local rocks
- increased argon gas content in the soil
- curious animal behaviour
how are earthquakes predicted?
it is very difficult and regions at risk can be identified through plate tectonics, fault lines can be monitored and local magnetic fields measured
how are earthquakes prevented?
it is almost impossible to prevent but there has been studies to stop plates sliding past each other
how can you be protected against earthquakes?
it means preparing for the event by modifying the human and built environments in order to decrease vulnerability
what is the Federal Emergency Management Agency?
they plan to promote understanding of earthquakes and their efforts, they work better to identify earthquake risk, to improve earthquake resistant design and construction techniques, and to encourage the use of earthquake safe policies
how is education helpful for earthquakes?
this is the main way that loss of life can be minimised, instructions are issued in how to prepare for events including securing homes and assembling earthquake kits
how can structures be made hazard resistant?
by putting a large concrete weight on top of the buildings which will move in the opposite direction to the force of the earthquake, putting large rubber shock absorbers in the foundations, and by adding cross-bracing to the structure to hold it together
how can fires be prevented?
smart meters have been developed that can cut off the gas if an earthquake of sufficient magnitude occurs
how can the emergency services help?
heavy lifting gear needs to be available and many people should be given first aid training
how can insurance help?
in richer areas, people are urged to take out insurance to cover their losses, the only problem being is that it is very expensive
how can aid help?
most aid to poorer countries has generally been to help in the few days after the event, providing medical services, tents, water purification equipment, and search and rescue
how can tsunamis be protected against?
they cannot be entirely predicted even if the location and magnitude is known, certain automated systems can be installed to give warnings
regions with a high tsunami risk use warnings to warn the population before the waves reach the land
