Earth Quakes - Frequently Asked Questions

Find answers to frequently asked questions (FAQ) about the Earth Quakes.

Q. Why don't you have the record of the earthquake which I felt?
A.

If the earthquake just happened a few minutes ago, you may have arrived at the webpage before our system has finished updating. If this is so, please check back in a few minutes to see if your event is now in place.

It may also be that you felt an earthquake just below the magnitude cutoff line. Generally, new maps are automatically made for quakes of magnitude 3.7 and greater (3 in certain urban areas). However, if you felt a smaller earthquake which is not on our site, please send in an unknown report. We review the unknown reports regularly and will post maps if people report on smaller quakes.

Q. Why isn't my zip code on the map?
A.

The maps are automatically generated to cover a preset distance from the epicenter of the earthquake. If you felt an earthquake but were some distance from the epicenter, your zip code may be off the borders of the map (although still counted in the total number of responses). If the earthquake is felt by a sizable number of people outside the original map range, a zoomed-out map may be made manually.

Q. This earthquake was a rolling one, but the one the other day was a jolt. Why the difference?
A.

The shaking you feel from an earthquake depends on the distance you are from the epicenter of the earthquake, the structure you are in, the type of material under the structure, and a variety of other factors. If you are close, the shaking will be more violent and "faster". If you are further away, the high-frequency "fast" shaking will have been "absorbed" into the earth's crust, and all that you will feel are the longer-period, more rolling motions. Furthermore, hard rock tends to shake less than softer sediment. Focussing and de-focussing of seismic energy can cause dramatic differences in the shaking between areas also. So it could have been any number of these factors or a combination of them that contributed to the difference in your experience of the earthquake.

Q. How long was the shaking?
A.

The duration of shaking you feel from an earthquake depends in part on the distance you are from the epicenter of the earthquake. If you are close, the shaking will be more violent, "faster", and may not last as long. If you are further away, the high-frequency "fast" shaking will have been "absorbed" into the earth's crust, you will feel are the longer-period, more rolling motions, and they may be of longer duration. In short, the duration is different in different places.