The focus is the place inside Earth’s crust where an earthquake originates. The point on the Earth’s surface directly above the focus is the epicenter. When energy is released at the focus, seismic waves travel outward from that point in all directions . ... It’s these waves that you feel during an earthquake.
What is the difference between focus and Hypocentre?
As nouns the difference between focus and hypocentre
is that focus is (countable|optics) a point at which reflected or refracted rays of light converge while hypocentre is (geology) the focus of an earthquake , directly under the epicentre.
What is the difference between the epicenter and the focus of an earthquake quizlet?
Focus is the first point of movement along a fault where all earthquake waves originate – it is below the surface. The epicenter is the point on the surface above the focus – the place on the surface that would receive the most intense vibrations.
How do you find the focus of an earthquake?
Another seismic wave used to determine focal depth is the sP phase – an S wave reflected as a P wave from the Earth’s surface at a point near the epicenter. This wave is recorded after the pP by about one-half of the pP-P time interval.
What is the difference between earthquake and aftershock?
But what is the difference? The difference is in the intensity of the quake . The initial quake always has the greatest power, or magnitude, as defined by the Richter scale. Aftershocks are smaller quakes that then occur in the general area after the main quake.
Where is the epicenter of the earthquake located?
The surface where they slip is called the fault or fault plane. The location below the earth’s surface where the earthquake starts is called the hypocenter, and the location directly above it on the surface of the earth is called the epicenter. Sometimes an earthquake has foreshocks.
Which represents the epicenter of the earthquake?
The epicenter is the point on the earth’s surface vertically above the hypocenter (or focus) , point in the crust where a seismic rupture begins.
Where do earthquakes show the most damage?
The epicenter is the point on the land surface that is directly above the focus. In about 75% of earthquakes, the focus is in the top 10 to 15 kilometers (6 to 9 miles) of the crust. Shallow earthquakes cause the most damage because the focus is near where people live.
Why do shallow focus earthquakes cause more damage?
Shallow quakes generally tend to be more damaging than deeper quakes . Seismic waves from deep quakes have to travel farther to the surface, losing energy along the way.
At what depth is the focus?
Shallow earthquakes are between 0 and 70 km deep ; intermediate earthquakes, 70 – 300 km deep; and deep earthquakes, 300 – 700 km deep. In general, the term “deep-focus earthquakes” is applied to earthquakes deeper than 70 km.
Why do we need to know the epicenter of an earthquake?
The main importance in determining the epicentre is so that the fault that ruptured causing the earthquake can be identified . ... If the fault is previously unknown (such as the 2010 Canterbury earthquake), then it is important because it means that the hazard models for the area need improvement.
What is intensity of earthquake?
The effect of an earthquake on the Earth’s surface is called the intensity. ... The Modified Mercalli Intensity value assigned to a specific site after an earthquake has a more meaningful measure of severity to the nonscientist than the magnitude because intensity refers to the effects actually experienced at that place .
Do many small earthquakes mean a big one is coming?
Scientists finally know how big earthquakes start: With many smaller ones . Faults likely weaken or change before a large earthquake , new research has found. The vast majority of earthquakes we feel come soon after smaller ones, according to new research that provides unprecedented insights into how seismology works.
Which country has the most earthquakes?
For which country do we locate the most earthquakes? Japan . The whole country is in a very active seismic area, and they have the densest seismic network in the world, so they are able to record many earthquakes.
Is the aftershock of an earthquake worst?
Aftershocks tend to be the most severe and happen more frequently in the hours and days that follow an earthquake. However, their magnitude and frequency decrease over time.
What happens to lag time the further you are from the epicenter?
Which of the statements best describes the relationship between lag time and distance from epicenter? The longer the lag time, the closer the distance. ... The shorter the lag time, the farther the distance. There is no relationship .
