Recent Earthquakes in Hawai`i
Recent Earthquakes in Hawai`i
To navigate through these maps you should start at the index map of our site. To navigate through these maps you should start at the index map of our site.
Once you have looked at the index map click on an area to zoom in. 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. 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 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 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 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 move to an adjacent map you can click on one of the blue arrows near the edges of the map. the edges of the map.
If you click on an earthquake (either on a map or in a list) and get 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 this a page of detailed information you should look at the bottom of this page for auxiliary information such as page for auxiliary information such as fault plane solutions. fault plane solutions.
At any time you can use your back button to return to a previous page, 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. but always remember the note above about reloading if a page seems old.
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We agree that circles are prettier than squares, and we anticipate
We agree that circles are prettier than squares, and we anticipate
that as software and hardware get better and faster, it will be more
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
feasible to use circles. Right now we have opted for the simplicity
and visual clarity of squares.
and visual clarity of squares.
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How can I zoom in further?
How can I zoom in further?
There are a variety of special maps listed on each page. These special
There are a variety of special maps listed on each page. These special
maps cover selected areas in greater detail.
maps cover selected areas in greater detail.
We can't allow arbitrary zooming in because this would mean creating
We can't allow arbitrary zooming in because this would mean creating
maps for each individual user and our servers could not handle that
maps for each individual user and our servers could not handle that
load.
load.
What pages should I bookmark?
What pages should I bookmark?
You may want to bookmark the index page
You may want to bookmark the index page
on the various mirror sites as well
on the various mirror sites as well
as the more detailed maps for the area where you live and work and
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
others that you find interesting. This may help you get fast access
after significant earthquakes when many people are trying to use the
after significant earthquakes when many people are trying to use the
Recent Earthquakes system.
Recent Earthquakes system.
Why are squares used for the earthquakes?
Why are squares used for the earthquakes?
Some users prefer to see earthquakes drawn as circles. We have chosen
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
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
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
a circle. To draw a good looking circle requires a technique called
anti-aliasing, however this introduces shades of grey into the image
anti-aliasing, however this introduces shades of grey into the image
which makes the map files larger and that makes them transfer more
which makes the map files larger and that makes them transfer more
slowly.
slowly.
How were the symbol sizes chosen?
How were the symbol sizes chosen?
Some users have noted that the magnitude 1, 2, and 3 earthquakes
Some users have noted that the magnitude 1, 2, and 3 earthquakes
are drawn with fairly small symbols. This was done because after
are drawn with fairly small symbols. This was done because after
a large earthquake there will be many small aftershocks. If the aftershocks
a large earthquake there will be many small aftershocks. If the aftershocks
have large symbols they may obscure the mainshock on the map.
have large symbols they may obscure the mainshock on the map.
To help prevent this we have made the small earthquakes have small symbols.
To help prevent this we have made the small earthquakes have small symbols.
How were the colors chosen?
How were the colors chosen?
Our goal was to highlight the earthquakes while also showing background
Our goal was to highlight the earthquakes while also showing background
information such as faults, roads, towns, and bodies of water. We limited
information such as faults, roads, towns, and bodies of water. We limited
our color choices by selecting from the approximately 200 "browser safe"
our color choices by selecting from the approximately 200 "browser safe"
colors that are consistently displayed without dithering by a variety of
colors that are consistently displayed without dithering by a variety of
web browsers. We also attempted to select colors that could be easily
web browsers. We also attempted to select colors that could be easily
distinguished by users with red-green color blindness.
distinguished by users with red-green color blindness.
Why don't the maps show topography?
Why don't the maps show topography?
Some of our older earthquake maps showed topography in the background
Some of our older earthquake maps showed topography in the background
as either a range of colors or shades of gray. Unfortunately,
as either a range of colors or shades of gray. Unfortunately,
this popular feature makes the map files about three times larger.
this popular feature makes the map files about three times larger.
These larger files take longer to transfer and at times of heavy
These larger files take longer to transfer and at times of heavy
usage can prevent us from serving many of those who want the
usage can prevent us from serving many of those who want the
earthquake information. While we would like to show the topography,
earthquake information. While we would like to show the topography,
we have concluded that it is more important to provide fast access
we have concluded that it is more important to provide fast access
to the earthquake data to as many people as possible.
to the earthquake data to as many people as possible.
What does "last 2 hours", "last 2 days" and "last 2 weeks" mean?
What does "last 2 hours", "last 2 days" and "last 2 weeks" mean?
Each map shows the time it was created. The phrases
Each map shows the time it was created. The phrases
"last 2 hours", "last 2 days", and "last 2 weeks" are with respect to
"last 2 hours", "last 2 days", and "last 2 weeks" are with respect to
that time. Any earthquakes that occurred within two hours of the
that time. Any earthquakes that occurred within two hours of the
creation time are in the "last 2 hours" and are colored red.
creation time are in the "last 2 hours" and are colored red.
Those that occurred between 2 and 48 hours before the map was created
Those that occurred between 2 and 48 hours before the map was created
are in the "last 2 days" and are colored blue. Those that occurred between
are in the "last 2 days" and are colored blue. Those that occurred between
48 hours and 14 days (336 hours) before the map was drawn are in the "last 2 weeks" and
48 hours and 14 days (336 hours) before the map was drawn are in the "last 2 weeks" and
are colored yellow.
are colored yellow.
How do the earthquakes get here?
How do the earthquakes get here?
Another page describes how the earthquake
Another page describes how the earthquake
information gets onto the web server.
information gets onto the web server.
Why do some earthquakes disappear?
Why do some earthquakes disappear?
The earthquake data shown here is automatically generated and despite
The earthquake data shown here is automatically generated and despite
our best efforts some glitches will create bogus earthquake locations
our best efforts some glitches will create bogus earthquake locations
and/or magnitudes. When we find a bogus event, usually by studying
and/or magnitudes. When we find a bogus event, usually by studying
the seismograms, we delete it and careful observers may notice that an
the seismograms, we delete it and careful observers may notice that an
earthquake has disappeared. This often happens after a large earthquake
earthquake has disappeared. This often happens after a large earthquake
when our systems don't realize that all of the seismograms were created
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
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
"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 bring the data from our seismometers to our computers create glitches
that also can create bogus events. For these reasons it is very
that also can create bogus events. For these reasons it is very
important to remember that this data is preliminary and when events
important to remember that this data is preliminary and when events
disappear they weren't real to begin with.
disappear they weren't real to begin with.
Why isn't the distance to the nearest fault provided?
Why isn't the distance to the nearest fault provided?
Seismologists evaluate the hypocenter location and the
Seismologists evaluate the hypocenter location and the
focal mechanism of an earthquake to decide if the earthquake occurs on a named fault. Research shows that many earthquakes occur on small, un-named faults located near well known faults. For example, most of the aftershocks of the 1989 M6.9 Loma Prieta earthquake occurred on small, subsidiary faults within a few hundred meters of the mainshock rupture plane. On other fault segments like the San Andreas fault near Parkfield, most of the earthquakes occur on the San Andreas fault. It is difficult to automate this decision process, and it would be misleading to imply on the basis of only distance that an earthquake occurs on a named fault.
focal mechanism of an earthquake to decide if the earthquake occurs on a named fault. Research shows that many earthquakes occur on small, un-named faults located near well known faults. For example, most of the aftershocks of the 1989 M6.9 Loma Prieta earthquake occurred on small, subsidiary faults within a few hundred meters of the mainshock rupture plane. On other fault segments like the San Andreas fault near Parkfield, most of the earthquakes occur on the San Andreas fault. It is difficult to automate this decision process, and it would be misleading to imply on the basis of only distance that an earthquake occurs on a named fault.
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