Introduction Implementation Basic Usage Map Controls Event Filtering Display Statistics Region Selection View in 3D
 

Introduction

The IRIS Earthquake Browser (IEB) is an interactive map for displaying selections of up to 25,000 seismic event epicenters (normally earthquakes) on a map of the world. There are millions of events to choose from.

These event selections can also be viewed in profile and freely rotated with the 3D Viewer tool. No plugins are required. They can also be viewed as sortable tables, exported to spreadsheet format and animated over time on the map.

A notable feature of the map is it can be bookmarked with (almost) all of its settings preserved in the bookmark, and thus can be emailed, socially shared, or just referred to later. Other websites can dynamically construct IEB URLs and thereby send people to a certain very specific place, time, and set of earthquakes. Here is an example.

IEB is intended to be easy-to-use and provide value as an educational tool and for some scientific research-related purposes.

Note: The terms "earthquakes", "quakes" and "events" may be used interchangeably in this document. The reason the word "events" is used is that human activities (bombs, demolitions, mining, etc), as well as phenomena like meteors, may also be detected, and there is no difference to a seismometer whether the cause was actually an earthquake or not.

 

Implementation

IEB is a Google map. By default, it uses earthquake data obtained about every 15 minutes from the USGS. IEB has accumulated about 3 million USGS earthquakes, dating from about 1970 to about an hour ago.

About small magnitudes in the U.S.

Though the default map event data are from the USGS, IEB also maintains a separate, extended database, which contains a mix of about 5.8 million earthquakes dating from same time range. See the Data Source option below.

 

Basic Usage

The user selects earthquakes to display on the map using filtering options like date, magnitude and depth ranges, along with choosing a priority for either the most recent or the largest magnitude earthquakes. Regions of interest can be selected by drawing a selection box on the map.

For practical reasons, only a small subset of the millions of earthquakes can be shown at a given time (currently up to 25,000). That is why a priority of newest vs. largest is needed. However, by zooming, panning and selecting regions, the user can quickly discover all of the earthquakes in the database for any region of the world.

When zooming and panning, the earthquakes displayed update dynamically. The filter options mentioned above are re-applied and the database re-queried as soon as the mouse (or finger on a tablet) is released -- to match the currently-visible boundaries of the map. With larger numbers of events this can cause a delay which is not convenient.

So the solution is this:
If you have selected a region of interest, then that set of earthquakes shown on the map is "locked", and zooming or panning will NOT cause a database update or delay. To resume dynamic updating deselect the region.

Region selections can be as tiny as a few kilometers square!

Tip: If your intention is to view the whole world, do not just make a huge selection box, instead simply deselect any region you may have selected and zoom out to where the whole world is visible. The first approach is one of the slowest database queries possible, and the second is the fastest.

Earthquakes shown or selected on the map may be viewed in a table, rotated in 3D or downloaded using the "View earthquakes as: Table or 3D", found in the Options panel.

The resulting table can be sorted by up to three of its columns. It can be copied, by double clicking it, and pasted into various editors and programs such as Excel. Direct exporting to CVS and NetCDF formats is also possible.

Browser Compatability:

Recent versions of Chrome, Safari and Firefox work best. All WebKit-based browsers tested work. Most recent tablets work, too.

Older versions of Internet Explorer do not work well with IEB, though the new Microsoft Edge browser (mid 2019) will likely work fine.

Finally, your computer's operating system, clock speed, available memory and Internet connection bandwidth will all impact performance.

 

Map Overview

The following diagram describes some of the features available in IEB:

  1. Zoom controls - Plus and minus buttons for zooming and and out.
    Pressing the "world" icon zooms all the way out at once.

    Depending on the dimensions of your window and device, if you are zoomed out as far as you can, you may see the world "wrap around" (e.g. Africa shown twice) -- this is normal for many Google maps.

    Tip: like most Google maps, you can hold the command key and scroll the mouse wheel to zoom, however this might be frustrating, since sudden, large jumps in zoom level often take place.
  2. Help - Brings you to the screen you are viewing now.
  3. Title - You can bookmark the map the way it looks now, with a custom title, which will appear next to the title and will be preserved in the bookmark. (Tip: wait until you are all ready to share/bookmark the map, since changing the settings or search criteria will delete the name.) Click on the words IRIS Earthquake Browser up top, and enter the custom name.
  4.  
     

    To save or share your map:

    • Make a bookmark via the browser in the customary way or
    • Drag the URL (web address) into an email, or any application that accepts dragged URLs. (This is the most visually attractive option) or
    • Press the tiny "clipboard" button (#11 in the diagram above) to copy the URL to your clipboard

  5. Options - A set of filtering options for determining the subset of available earthquakes to display. After making changes press the Apply button to see the result by requerying the database.
  6. Earthquake Count - Shows how many earthquakes are displayed currently on the map, versus how many could have been displayed if the limits of the "Maximum earthquakes" were not enforced. If you have selected a region and then zoomed in closer than the region's size, or panned away from the region, the number visible will only include those actually visible on the map in the current view.
  7. Show plate boundaries - Color coded plate boundaries can be turned on and off here.
  8. Animate the earthquakes - The earthquakes are displayed as a series, moving forward or backward in time instead of all at once. You can speed up or slow down or pause the animation, or drag the control handle forward and backward in time. Loop the animation by selecting the loop checkbox.
  9. Go to a new Region/Topic - Select from various predefined maps for interesting or large seismic events which have been bookmarked and given titles, as described already above, and which demonstrate the ability to make topical maps of such things as the Asian Tsunami's aftershocks, or mysterious clusters of events. Going to a region in this way will wipe out any settings, including any map title, and reset them to those of the new predefined region, but the browser "back" button will restore them, and of course they can be bookmarked as well.
  10.  
  11. View earthquakes as a table or in 3D - Clicking on an earthquake on the map shows a limited window showing the closest 10 events to the one you clicked on.

    For a much more complete list of the data on the map use the Table link. All the map data come up in a table with sortable columns in its own window so you can peruse and sort it in various ways.
     
    Also, from here you can view the dataset in pseudo-3D, allowing rotation and a number of functionals from its own menu, such as "Look North", "Scale the events down, visually", and other cosmetic tricks.
  12. Download as: Excel or NetCDF - This will cause an immediate download of the data to your hard drive. (NetCDF is a binary data format used by many scientists.)
  13. Copy current URL to clipboard - Puts the current web address (URL) of the map as it appears, into your clipboard, so you can paste it into another document, say an email or PowerPoint.
  14. Navigation Information - Displays the lat/lon bounds of the current selection and the lat-lon coordinates of the cursor.
  15. Map Views - Select from various Google map view modes such as Satellite, plain Map, or Map (with terrain).
  16. Magnitude Scale - Circle sizes indicate earthquake magnitudes.
  17. Depth Scale - Circle colors indicate the depths of earthquakes (kilometers)
  18. Region Selection - Use this to select a map region and then (usually) zoom into it. Only events in the selected region will be displayed. The boundaries can be adjusted by dragging on the corners, in most cases, right after making a selection.

    As soon as you make a selection, two new options "Zoom to Region" and "Deselect Region" appear. More on that below.
 

Event Filtering Controls

Be sure to press Apply after making changes!

Earthquake miltering determines which earthquakes from the database are shown at any given time. The events you get are filtered in two ways:

  1. By the max number of and preferred size priority
  2. By the filters in (blue), relating to Time, Magnitude and Depth ranges

The first two options, Maximum earthquakes: and Select earthquakes by: , determine the number of earthquakes and which of the millions available will be displayed on the map. The rest of the options further restrict ranges of time, magnitude and depth to affect what is displayed. You will be prompted to press Apply when you make changes to these settings.

Options Maximum earthquakes: and Select earthquakes by: are always shown. To reveal the other options you must click on their option names ( blue").

Maximum earthquakes: determines the maximum number of quakes that will be shown in any given view. You can choose values between 10 and 25,000.

Note: displaying too many quakes can cause some web-browsers or tablets to be slow or unresponsive. Try 5,000 and 10,000 before going higher.

Time Range: determines the dates of the earthquakes that will be shown. By default, all available dates are used: Earliest Available to Latest Available.

To use your own date range, uncheck one or both of the checkboxes and enter dates in the text fields or the date picker popups. Dates are in Universal Time (UTC) and run midnight to midnight.

Magnitude Range: determines the magnitudes of the earthquakes that will be shown. By default, all available magnitudes are used.

To use your own magnitude range, uncheck the checkbox and enter values in the text fields.

Depth Range: determines the depths of quakes that will be shown. By default, all available depths are used.

To use your own depth range, uncheck the checkbox and enter values in the text fields.

 

Data Source: IEB uses USGS data by default. If you wish to see more events, IRIS has a much larger database, from mixed sources, mainly the USGS plus the ISC.

Data Source options:
USGS - Single source. Greater reliability of location and magnitude, but fewer small earthquakes outside N. America
MIXED - Multiple sources including International Seismological Centre and USGS. Some locations and magnitudes are less reliable, but includes more smaller earthquakes and man-made events worldwide.

 

Earthquake Count Field

The Earthquake Count shows how many quakes were retrieved from the database, along with the total number of that could have been retrieved (but the limits of Maximum earthquakes setting prevented it). Since zooming and panning can hide some of the earthquakes, the number that are actually visible in the current map view is also given.

If the Earthquake Count reads "500 of 38738" then 500 quakes are on the map and 38,738 - 500 = 38,238 matched in the database but are not displayed. So although a huge number of quakes matched your Options filter, they were not retrieved, based on the Max quakes setting of 500. Which 500 of them were retrieved is based on the "Select Earthquakes By" setting.

If the counts are positive, but the number visible is zero, pan, zoom out, or use "Zoom to Region" if a region is currently selected. IEB prompts you if this condition arises. If all the values are zero, relax your filter settings in Options and press Apply.

If you have selected a region using "Select New Region", then zooming and panning will not affect the set of earthquakes displayed, the set is "locked" until you either deselect the region or change filter options in the above right and press Apply.

 

Region Selection Controls

The region selection control allows you to quickly select a region and zoom there. Only events in the selected region will be shown.

To start, click Select New Region.

The cursor changes to a crosshair. Now drag from one corner to the opposite corner of the desired region and release.

Press the ESC key to cancel out of region select mode.

The event filter options will be freshly applied, but to the selected region only.

Next click Zoom to Region to zoom to the selected region.

When a region is selected, the events inside it are effectively 'frozen'. If you pan the map away or zoom too close, no events will be visible -- but IEB recognizes this condition and will prompt you what to do.

Click Deselect Region to remove the selection box and 'unfreeze' the events, so they once again auto update to reflect the visible map area as you zoom and pan.

You can immediately select a new region without deselecting the current one first.

 

Viewing and rotating a set of Earthquakes in 3D

IEB allows you to rotate thousands of earthquakes in any direction as well zoom in and out. It allows a better understanding of the spatial relationships in a set of earthquakes and often reveals a fault line or other underground feature only visible from a side view.

It will show coastline and plate boundaries and has a selection of view options to help visualize seismicity in emulated 3D space. It is very simple to use, and it requires no browser plugin.


animated gif: rotating earthquakes in 3D near Fiji Islands

After selecting a region of interest, in this case, the Fiji Islands region, you simply press the
3D View link:

A new browser window (or tab) with a black background opens up.

By dragging your mouse you can rotate the scene.

With the mouse wheel you can zoom in and out.

There are various settings and view-related commands in the View menu such as auto-rotation, scaling, and capturing a screenshot.

We thank the USGS, the NSF and IRIS Consortium members for data, funding and support; and original author B. Weertman.