What is the difference between an earthquake's focus and its epicenter?
AThey are the same thing — both refer to where the earthquake happens
BThe focus is the point underground where the rock first slips; the epicenter is the point on the surface directly above the focus
CThe epicenter is underground; the focus is on the surface
DThe focus is where the earthquake is strongest; the epicenter is where it is weakest
The focus (or hypocenter) is the actual point within the Earth where the fault rupture begins. The epicenter is the point on the Earth's surface directly above the focus. The focus can be shallow (a few kilometers deep) or deep (up to about 700 km), and this depth affects how the earthquake is felt at the surface.
Question 2 Multiple Choice
If earthquake A has a magnitude of 5 and earthquake B has a magnitude of 7, earthquake B released about how many times more energy?
A2 times more
BAbout 32 times more
CAbout 1,000 times more
DAbout 100 times more
Each whole number increase in magnitude represents roughly 32 times more energy released. From 5 to 6 is about 32 times. From 5 to 7 is about 32 x 32, which is roughly 1,000 times more energy. Magnitude is logarithmic, which is why the difference between a 5 and a 7 is so enormous.
Question 3 True / False
Scientists can predict exactly when and where the next major earthquake will occur.
TTrue
FFalse
Answer: False
Scientists can identify regions with high earthquake risk (based on fault locations, plate boundaries, and historical patterns) and can estimate the probability of an earthquake in a given area over decades, but they cannot predict the specific day, time, or precise location of future earthquakes. Earthquake prediction remains one of the great unsolved challenges in earth science.