Questions for Notes on Section 2-3 of the Textbook

Questions for Notes on Section 2-3 of Textbook
1a.What is a seismograph?
A seismograph is an instrument that is used to monitor, record, and examine and movements in the Earth’s crust. Seismographs and fault-monitoring devices provide data used to map faults and detect changes along faults. Geologists are also trying to use this data to develop a method of predicting earthquakes. The typical seismograph consists of some sort of base which absorbs the ground motion from the seismic waves of the earthquake. The top of it has a wire that hangs straight down and is attached to a pen with a weight that keeps the pen straight. Right on the tip of the pen is a rotating drum with a roll of paper that records the earthquake’s seismic waves which are produced by the seismograph. This is called a seismograph.
1b. How does a seismograph record waves?
A seismograph records waves with its rotating drum. The base absorbs the vibrations of the seismic waves, which then affect the whole seismograph. The pen is kept still by the weight it’s attached to, and the seismogram is recorded.
1c. A seismograph records a strong earthquake and a weak earthquake. How would the seismograms for the two earthquakes compare?
The seismogram for the stronger earthquake would have a bigger difference between the crests and troughs. The stronger earthquake also has more amplitude and more powerful waves recorded. The weaker seismic waves would cause a smaller disturbance and make much less stressed data.

2a. What four instruments are used to monitor faults?
The four instruments used to monitor faults are tilt meters, creep meters, laser-ranging devices, and GPS satellites. There is something different that each one measures, and they all have their own way of measuring the movement around them.

2b. What changes does each instrument measure?
Tilt meters measure the tilting or raising of the ground, or any vertical movement. The way the tilt meter works is with a water-level scale. Inside the scale is water, and whenever there is the slightest movement a little bit of water pours from one into the other. Creep meters measure the horizontal movement of the ground. With creep meters, there is a wire stretched across a fault and attached securely to one side. On the other side, there’s a weight. By using the measuring scale to tell how much the weight was moved, scientists can tell how much horizontal movement there was. Laser-Ranging devices are really simple – they use laser beams to detect horizontal fault movements. They consist of a laser beam, a laser reflector, and an observatory housing a laser. Lastly, GPS satellites are used very often. They orbit the earth to measure changes in elevation and tilt of the land as well as horizontal movement along a fault. Standing for the “global positioning system”, GPS satellites were developed to help ships and planes find their routes, and were more recently used for monitoring faults.

2c. A satellite that monitors a fault detects an increasing tilt in the land surface along a fault. What could this change in the land surface indicate?
An increasing tilt in the land surface along a fault is evidence that there might be an earthquake. This also refers to stress, because an increasing tilt in the land surface generally means that there is compression in that area. In many years, that fault may turn into a mountain range.


3a. What are three ways in which geologists use seismographic data?
The first and main way that geologists use seismographic data is to detect and attempt to predict earthquakes. This can be helpful for the entire world, and although there is no sure system of how to predict earthquakes geologists are getting there. Secondly, it’s also important for geologists to figure out how to map faults. This way, they know where most earthquakes will be, and seismographic data can help with that. A third way that geologists and scientists use seismographic data is to monitor the changes along faults that they have already discovered and mapped out. There is connection with this to predicting earthquakes, because by monitoring any changes in elevation, tilting of the land surface, or ground movements along faults, it’s much easier to discover whether there will most likely soon be an earthquake or not.

3b. How do geologists use seismographic data to make maps of faults?
When seismic waves encounter a fault, the waves are reflected off. Geologists use this data to map the fault’s length and depth. Faults are often hidden by a thick layer of rock and soil, so mapping hidden faults is very important.


3c. Why do geologists collect data on friction along the sides of faults?
Geologists collect data on friction along the sides of faults so that they can figure out which areas need to be watched for any disturbances that could possibly lead to an earthquake. With a high amount of friction the tension builds up in the fault, so it is much more likely to lead to an earthquake. With a very low amount of friction, everything is normal and no tension will be created.