     |
|
Recent Earthquakes in the Intermountain West
Recent Earthquakes FAQ (Frequently Asked Questions)
- It currently presents data from the University of Utah seismograph network and will expand to include other networks.
- It offers complete network coverage with no gaps because of an overlapping system of maps.
- It provides text information on each earthquake and auxiliary information on some of them.
- How do I find what I want?
- How can I zoom in further?
- What pages should I bookmark?
- Why are squares used for the earthquakes?
- How were the symbol sizes chosen?
- How were the colors chosen?
- Why don't the maps show topography?
- What does "last hour", "last day" and "last week" mean?
- How do the earthquakes get here?
- Why do some earthquakes disappear?
- What are the future plans for this system?
How do I find what I want?
NOTE: Our information changes with time. Sometimes when you look at a page your browser will show you an old copy that it has cached. Check the time on the page and in the map. If it was produced over an hour ago, or if you think something has happened since it was produced, then use the reload feature of your browser to get a new version of the file.To navigate through these maps you should start at the index map or see our list of other sites in the region.
Once you have looked at the index map, click on an area to zoom in. Or, you can select one of the lists of earthquakes below the map.
If you click on the index map and zoom in, you can get more information on any earthquake by either clicking on its map symbol or by clicking on its summary information presented in a list below the map. Or, to move to an adjacent map, you can click on one of the blue arrows near the edges of the map.
If you click on an earthquake (either on a map or in a list) and get a page of detailed information, you should look at the bottom of the page for auxiliary information such as fault plane solutions.
At any time you can use your back button to return to a previous page, but always remember the note above about reloading if a page seems old.
Return to top of faq
Return to top of faq
Return to top of faq
We agree that circles are prettier than squares, and we anticipate
that as software and hardware get better and faster, it will be more
feasible to use circles. Right now, we have opted for the simplicity
and visual clarity of squares.
Return to top of faq
Return to top of faq
Return to top of faq
Return to top of faq
Return to top of faq
Return to top of faq
Return to top of faq
Recent Earthquakes home page.
How can I zoom in further?
There are a variety of special maps listed on each page. These special
maps cover selected areas in greater detail.
We can't allow arbitrary zooming in because this would mean creating
maps for each individual user and our servers could not handle that
load.
What pages should I bookmark?
You may want to bookmark the index page, as well
as the more detailed maps for the area where you live and work and
others that you find interesting. This may help you get fast access
after significant earthquakes when many people are trying to use the
Recent Earthquakes system.
Why are squares used for the earthquakes?
Some users prefer to see earthquakes drawn as circles. We have chosen
to use squares, because computer screens are based on a square grid of
dots or rasters. This makes it easier to draw a clear square than
a circle. To draw a good looking circle requires a technique called
anti-aliasing, however this introduces shades of grey into the image
which makes the map files larger. That makes them transfer more
slowly.
How were the symbol sizes chosen?
Some users have noted that the magnitude 1, 2, and 3 earthquakes
are drawn with fairly small symbols. This was done because after
a large earthquake there will be many small aftershocks. If the aftershocks
have large symbols, they may obscure the mainshock on the map.
To help prevent this, we have made the small earthquakes have small symbols.
How were the colors chosen?
Our goal was to highlight the earthquakes while also showing background
information such as faults, roads, towns, and bodies of water. We limited
our color choices by selecting from the approximately 200 "browser safe"
colors that are consistently displayed without dithering by a variety of
web browsers. We also attempted to select colors that could be easily
distinguished by users with red-green color blindness.
Why don't the maps show topography?
Some of our older earthquake maps showed topography in the background
as either a range of colors or shades of gray. Unfortunately,
this popular feature makes the map files about three times larger.
These larger files take longer to transfer and, at times of heavy
usage, can prevent us from serving many of those who want the
earthquake information. While we would like to show the topography,
we have concluded that it is more important to provide fast access
to the earthquake data to as many people as possible.
What does "last hour", "last day" and "last week" mean?
Each map shows the time it was created. The phrases
"last hour", "last day", and "last week" are with respect to
that time. Any earthquakes that occurred within one hour of the
creation time are in the "last hour" and are colored red.
Those that occurred between 1 and 24 hours before the map was created
are in the "last day" and are colored blue. Those that occurred between
24 hours and 7 days (168 hours) before the map was drawn are in the "last week" and
are colored yellow.
How do the earthquakes get here?
Another page describes how the earthquake
information gets onto the web server.
Why do some earthquakes disappear?
The earthquake data shown here is automatically generated and, despite
our best efforts, some glitches will create bogus earthquakes. When we
find a bogus event, usually by studying the seismograms, we delete it
and careful observers may notice that an earthquake has disappeared.
This often happens after a large earthquake when our systems don't
realize that all of the seismograms were created by a single event. In
this case, one earthquake will turn into multiple "events" on the
maps. In other cases, problems in our telemetry systems that bring the
data from our seismometers to our computers create glitches that also
can create bogus events. For these reasons, it is very important to
remember that this data is preliminary and when events disappear they
weren't real to begin with.
What are the future plans for this system?