Mod 6.3 - Prediction and Prevention (Earthquakes and ECLs) Flashcards
Ground movement detectors
A seismograph is a recording device that detects ground motion due to movements in the crust. Typically, this will comprise a recorder and a seismometer, which is a sensor that detects the velocity of the ground. Seismometers are usually very sensitive, allowing them to pick up very minor tremors that otherwise wouldn’t be felt. These tremors may be a sign that a larger earthquake may be coming, however this is not always the case.
Anomalous animal behaviour
It is a popular hypothesis that some animals can detect earthquakes and behave abnormally in response, since they can detect the P-wave vibrations of an earthquake that humans cannot feel. Throughout history, there have been many written or oral reports of unusual animal behaviour before an earthquake. However, this is unreliable data as most papers consist of single observation and anecdotes that cannot be tested rigorously, and thus there are not enough valid tests to confirm or reject the hypothesis. Thus, anomalous animal behaviour is not a reliable or effective method of earthquake prediction.
Strainmeters
Strainmeters are sensitive instruments that can detect very tiny changes in pressure. Such changes provide information about the ‘strain’ building up in the crust that could lead to an earthquake. Strainmeters are usually installed in boreholes near active fault lines to provide information on areas where an earthquake is possible to occur based on tension in the crust. However, we are unable to detect when the strain will break.
Assess these technologies
The commonality with all these technologies is that while they ‘may’ provide evidence for an impending earthquake, it is by no means a sure thing. Seismographs detect many small ground movements all the time and they are not all signs of a large future earthquake. Anomalous animal behaviour is a hypothesis and has not been tested rigorously enough to confirm its reliability. Strainmeters can provide a clue that an earthquake may happen in the future but exactly when that will happen isn’t possible to say. It is for these reasons that earthquakes are so hard to predict - at best scientists can talk about probabilities or likelihoods or potential time frames for future earthquakes, but they cannot say for sure, exactly when and where an earthquake will happen. Therefore, these technologies are only somewhat effective, as they are unable to provide precise details about future earthquakes.
Temperature for ECLs
A large temperature gradient between the air of a low pressure system and warm sea surface temperatures is key in the development of an east coast low. Sea and air temperatures are measured by automated weather stations and buoys and are sent to the BOM for analysis. Temperature readings alone are ineffective in predicting ECLs, and must be combined with other information such as wind speed and pressure to analyse the likelihood of an ECL developing.
Pressure for ECLs
Atmospheric pressure is the force per unit area exerted by the weight of the atmosphere. It is measured by a barometer. Meteorologists use barometers to predict changes in the weather. A rapid drop in atmospheric pressure means that a low-pressure system is arriving. Low pressure means that there isn’t enough force, or pressure, to push clouds or storms away. A rapid increase in atmospheric pressure pushes that cloudy and rainy weather out, clearing the skies and bringing in cool, dry air. ECLs occur when a low pressure system develops along the eastern coast of Australia, and interacts with warm water from the East Australian Current. If a HPS develops to the south and blocks the LPS from moving away, this may lead to severe damaging winds and cause an ECL. Meteorologists can use barometers and temperature data to see signs of a developing east coast low up to a week in advance
