Recent earthquakes

Introduction
Earthquake Summary
Interactive Map
Google Earth
Earthquake Catalog
FAQ

AVO uses its extensive seismic network to locate as many as 9000 earthquakes per year near volcanoes in Alaska. Some earthquakes are associated with volcanic eruptions. Many others are part of normal background behavior in a geologically active region. Earthquakes are often one of the first signs that a volcano is becoming restless. Deviations from background seismic levels are monitored closely for eruptive potential. The list of earthquake details, the so-called earthquake catalog, can be browsed in multiple forms described below. Each earthquake in the catalog has been reviewed by an AVO seismologist. Because these are reviewed earthquakes it may take up to a few days for events to be included in the catalog. During notable earthquake swarms, AVO concentrates on the largest earthquakes first, often reviewing smaller earthquakes at a later point. In places where the seismic stations are numerous and close together (such as Mt. Spurr or Augustine), we are able to locate smaller earthquakes. Because we focus our coverage on volcanoes with the highest risk and eruption potential, our ability to detect small earthquakes varies considerably from place to place.

All times are given in UTC. Alaska Standard Time is 9 hours behind UTC (8 hours during daylight savings). Magnitudes are given as "ml" using a local magnitude algorithm.

For questions, read the FAQ at the bottom of this page.

This figure summarizes earthquake activity at volcanoes monitored by AVO. For each volcano, there is one bar per week for each of the past four weeks. As discussed above and in the FAQ, located earthquakes are just one type of data used to monitor volcanoes. At the Observatory we simultaneously watch many different slices of the data in order to detect emerging unrest as early as possible.

Earthquakes can be added to the Interactive Map by clicking the Recent earthquakes box. Each earthquake is marked by a small circle whose size is scaled by the quake magnitude and whose color is scaled by depth. There is a depth and color legend on the left panel. Clicking on an event opens a balloon with earthquake details. It is possible to pan and zoom this map to any desired view. This earthquake catalog includes the last 30 days, or the last 250 earthquakes, located by AVO. Views to individual volcanoes may be selected from the pull down menu. Use the check boxes to turn on other datasets including volcano locations, webcams, and seismogram displays. For a more interactive interface to the earthquake data, consider the Google Earth link below.

Go to AVO interactive map

For Google Earth users, AVO provides an interface to the past 30 days of seismic activity at Alaska volcanoes. By opening the link below, a feed to AVO's recent earthquake catalog will be added to your Google Earth menu. This link only needs to be read into Google Earth once. Once loaded, it will refresh periodically to keep the list of earthquakes up to date.

Each earthquake is represented by a circle (see figure). The legend in the top left shows how the icons' size and color relate to magnitude and depth, respectively. For more detailed information, an earthquake can be selected to show the exact time, latitude, longitude and depth of the quake. If enabled, at the top of the screen there is a slider bar which allows users to select specific time windows and to play the earthquakes through time like a movie. The time slider bar is a great tool for tracking how seismic activity has changed in recent weeks. Under the Places menu on the left, there are directories for each day's earthquakes. There is also a Views by volcano directory where users can select a volcano view. To add volcano names to the display, consider downloading the Global Volcanism Program's Volcano Placemarks.

Get AVO recent earthquakes (.kmz file): http://www.avo.alaska.edu/eq/kml/AVOquakes.kmz

To download the most recent version of Google Earth: http://earth.google.com/

The archive of earthquakes at Alaska volcanoes is available in several formats. This catalog contains all of the volcano earthquakes for which AVO has been able to determine a reliable location, beginning in October 1989. Because each earthquake in the catalog has been reviewed by an AVO seismologist, the data may have a latency of days to months. AVO's seismic network has expanded considerably in the past two decades. In the early 1990s, catalog coverage is limited to the Cook Inlet region. Though the recent catalog includes more than half of the historically active volcanoes throughout the state, there are still notable gaps in coverage. Users are strongly encouraged to consult AVO's published catalog descriptions for complete descriptions of the network coverage and seismic activity. The catalog summaries can be found at AVO Volcano Seismicity Catalogs.

Custom data requests are available through the AVO earthquake catalog search page. The catalog search is oriented toward research users and is hosted off-site. Data are available in several formats and, if requested, include phase pick information.

I see a large swarm of earthquakes at volcano _______. Does this mean it is going to erupt?

• Every volcano has its own distinct behavior. Many have routine earthquake swarms that are unrelated to eruptions. These swarms may be caused by hydrothermal systems, regional stresses in Earth's crust, or even the slow collapse of the volcanic edifice. Most seismic swarms are not precursors to eruptions. To determine whether a seismic swarm might foretell an eruption, AVO combines seismic data with satellite imagery, deformation, gas measurements and the geologic history of the volcano. Putting all of these data streams together, the Observatory has an excellent track record of predicting impending eruptions.

I see lots of activity on the helicorder for volcano _______. Why don't I see any earthquakes?

• There are several possibilities: (1) the helicorder is showing wind or electronic noise and not earthquakes; (2) the review of these earthquakes has not yet been completed by an AVO seismologist so they are not yet in the catalog; (3) There are many types of seismic activity at volcanoes other than earthquakes. It is possible that the seismic activity consists of volcanic tremor, explosions or rock falls; or (4) the earthquakes are large enough to be detected, but too small to be located.

The news is reporting a major earthquake in the Aleutians. Why can't I see it in the catalog?

• AVO's seismic network is optimized to monitor volcanoes in Alaska. Large non-volcanic earthquakes are monitored by the Alaska Earthquake Information Center. These two organizations work closely to provide comprehensive seismic monitoring across the region.

How can I tell which earthquakes happened a few weeks ago and which earthquakes are new?

• The date and time of an earthquake can be viewed by clicking on the circle icon. On the interactive map there is no way to explicitly limit which dates are being plotted. In the Google Earth interface, a recent date range can be selected using the time slider bar, or by toggling specific dates in the Earthquakes directory.

The depth scale on the legend extends to several hundred kilometers. Do earthquakes occur this deep?

• They do. However, rarely do earthquakes of volcanic significance extend deeper than about 50 kilometers. We use a scale that is compatible with all types of earthquakes observed on Earth. In some subduction zones, earthquakes occur as deep as 700 km, though in Alaska they almost never exceed 250 km.

How accurate are the earthquake locations?

• The accuracy of the locations varies considerably depending on the density of the local seismic network, station outages, weather (background noise) and the style of the earthquake. Earthquakes in dense areas of the network may be good to within a few hundred meters. Poor quality earthquakes, or limited network coverage may result in errors of a few kilometers. Generally, if AVO is not confident about an earthquake's location to within 5 km, the earthquake is excluded from this catalog.