When an earthquake occurs, two types of sound waves are generated and travel through the earth. The primary, or P, wave has a speed of about 10.5 km/s and the secondary, or S, wave has a speed of about 5.5 km/s. A seismograph, located some distance away, records the arrival of the P wave and then, 140 s later, records the arrival of the S wave. Assuming that the waves travel in a straight line, how far is the seismograph from the earthquake?

Comments (1)

i get that like they detect vibrations but do scientist set up sensors around the earth? how else could the machine detect earthquakes all over the world?

Comments (3)

A) The epicenter is calculated after the all the aftershocks of an earthquake are plotted. It is the statistical center of the earthquake. The focus is the spot of first motion of the rocks.
B) The epicenter is where the energy is first released and the focus of the earthquake is where most of the damage is done
C) The focus of the earthquake is were surface waves are first detected while the epicenter is where the P and S waves are detected.
D) The epicenter is the spot on the Earth’s surface directly above the focus.

Comments (1)

Following Hurricane Katrina in 2005, there became a strong concern in this country
about our ability to cope with natural disasters. Due to the expensive cost of
acquiring detailed data about the hazard before, during and after the event, many
agencies are putting systems forth to allow citizens affected by the events to
contribute details about their surroundings. This may be in the form of data sent
over a mobile phone, or Internet connection to a PC. Please weigh in your thoughts
about using this system as a method of coping with natural disasters by taking this
brief survey.
* 1. Have you ever experienced a natural disaster?
Yes
No
2.
Which of the following hazards have you experienced?
Flood
Hurricane
Earthquake
Fire
Tornado
None
3.
About at what intensity did the disaster occur?
Very low
low
moderate
high
very high
* 4.
Did you have access to the internet following the event
Yes
No
5.
As the event passed, did you feel that adequate updates about the hazard were
provided to affected citizens?
Yes
No
* 6.
Following the event, did you feel coherent enough that you would be able to
communicate in detail about your surroundings?
Yes
No
* 7.
Have you ever contributed Geospatial Information about a hazard or extreme event
online? (Through Google Earth, USGS website, Weather channel, etc..)
Yes
No
* 8.
Do you have any experience using a GPS system?
Yes
No
* 9.
Do you feel that your community has an adequate emergency response system in
place for the onset of natural disasters?
Yes
No
10.
Do you feel that GIS and Remote Sensing is a very appropriate way of coping with a
natural disaster before, during and after the onset of a natural hazard
Yes
No

Comments (1)

Following Hurricane Katrina in 2005, there became a strong concern in this country
about our ability to cope with natural disasters. Due to the expensive cost of
acquiring detailed data about the hazard before, during and after the event, many
agencies are putting systems forth to allow citizens affected by the events to
contribute details about their surroundings. This may be in the form of data sent
over a mobile phone, or Internet connection to a PC. Please weigh in your thoughts
about using this system as a method of coping with natural disasters by taking this
brief survey.

* 1. Have you ever experienced a natural disaster?
Yes
No
2.
Which of the following hazards have you experienced?
Flood
Hurricane
Earthquake
Fire
Tornado
None
3.
About at what intensity did the disaster occur?
Very low
low
moderate
high
very high
* 4.
Did you have access to the internet following the event
Yes
No
5.
As the event passed, did you feel that adequate updates about the hazard were
provided to affected citizens?
Yes
No
* 6.
Following the event, did you feel coherent enough that you would be able to
communicate in detail about your surroundings?
Yes
No
* 7.
Have you ever contributed Geospatial Information about a hazard or extreme event
online? (Through Google Earth, USGS website, Weather channel, etc..)
Yes
No
* 8.
Do you have any experience using a GPS system?
Yes
No
* 9.
Do you feel that your community has an adequate emergency response system in
place for the onset of natural disasters?
Yes
No
10.
Do you feel that GIS and Remote Sensing is a very appropriate way of coping with a
natural disaster before, during and after the onset of a natural hazard
Yes
No

What state are you located in?

Comments (2)

we were give a puzzle problem to solve and here it is..

"And the Earth Moved"
Seismographs are sensitive instrument for detecting earthquakes. They consists of large mass suspended by springs. When an earthquake happens, the disturbance travels through the earth, making the instrument vibrate. However, the mass tends not to move because of its inertia. This difference in movement is simplified and written out as a trace.

can you explain why most places in the world receive two traces for each single earthquake event? Can you also explain why a few places detect only one?

Thanks in advance 🙂

Comments (3)

Following Hurricane Katrina in 2005, there became a strong concern in this country
about our ability to cope with natural disasters. Due to the expensive cost of
acquiring detailed data about the hazard before, during and after the event, many
agencies are putting systems forth to allow citizens affected by the events to
contribute details about their surroundings. This may be in the form of data sent
over a mobile phone, or Internet connection to a PC. Please weigh in your thoughts
about using this system as a method of coping with natural disasters by taking this
brief survey.

* 1. Have you ever experienced a natural disaster?
Yes
No
2.
Which of the following hazards have you experienced?
Flood
Hurricane
Earthquake
Fire
Tornado
None
3.
About at what intensity did the disaster occur?
Very low
low
moderate
high
very high
* 4.
Did you have access to the internet following the event
Yes
No
5.
As the event passed, did you feel that adequate updates about the hazard were
provided to affected citizens?
Yes
No
* 6.
Following the event, did you feel coherent enough that you would be able to
communicate in detail about your surroundings?
Yes
No
* 7.
Have you ever contributed Geospatial Information about a hazard or extreme event
online? (Through Google Earth, USGS website, Weather channel, etc..)
Yes
No
* 8.
Do you have any experience using a GPS system?
Yes
No
* 9.
Do you feel that your community has an adequate emergency response system in
place for the onset of natural disasters?
Yes
No
10.
Do you feel that GIS and Remote Sensing is a very appropriate way of coping with a
natural disaster before, during and after the onset of a natural hazard
Yes
No

What state are you located in?

Thank you for your contribution

Comments (2)

* 1. Have you ever experienced a natural disaster?
Yes
No
2.
Which of the following hazards have you experienced?
Flood
Hurricane
Earthquake
Fire
Tornado
None
3.
About at what intensity did the disaster occur?
Very low
low
moderate
high
very high
* 4.
Did you have access to the internet following the event
Yes
No
5.
As the event passed, did you feel that adequate updates about the hazard were
provided to affected citizens?
Yes
No
* 6.
Following the event, did you feel coherent enough that you would be able to
communicate in detail about your surroundings?
Yes
No
* 7.
Have you ever contributed Geospatial Information about a hazard or extreme event
online? (Through Google Earth, USGS website, Weather channel, etc..)
Yes
No
* 8.
Do you have any experience using a GPS system?
Yes
No
* 9.
Do you feel that your community has an adequate emergency response system in
place for the onset of natural disasters?
Yes
No
10.
Do you feel that GIS and Remote Sensing is a very appropriate way of coping with a
natural disaster before, during and after the onset of a natural hazard
Yes
No

What state are you located in?

Thank you for your contribution

Comments (2)

I heard about this but I’m not sure how they have an impact on the Earth’s axial rotation. They said these earthquakes cause the Earth to speed up in axial rotation and there was one today; I hope to God and in my heart, no innocent people were caught in it. That would be bad. Would we have to skip a second or make them internally shorter on the other hand?

Comments (1)

how and why the behavior of seismic body waves changes at the different boundaries within
the Earth (refraction, reflection).

Comments (1)