![]() ![]() Screenshot of the Aftershock Forecast for an earthquake in Alaska, with the “Forecast” tab selected. If it is unlikely that there will be any aftershocks of that magnitude during that time frame, the table shows an asterisk, which means that an earthquake is possible but with a low probability. The second table shows the likely number of aftershocks above a certain magnitude and within a certain time frame, given as range of numbers which represents the uncertainty of the forecast. ![]() The first table shows the probability of at least one aftershock above a certain magnitude and within a certain time frame. The Forecast tab presents the forecast as tables, covering a range of aftershock magnitudes and time frames. Screenshot of the Aftershock Forecast for an earthquake in Alaska, with the “Commentary” tab selected.įorecast Tab: Tables Showing the Detailed Forecast The subsequent information is a simple summary of the forecast, followed by what has already happened, and ending with a more quantitative version of the forecast. The Commentary tab describes the aftershock forecast in simple language, starting with the concept that larger earthquakes could follow and that aftershocks will be continuing for some time and some safety information is included. The “Aftershock Forecast” card is at lower center.Ĭommentary Tab: A Starting Point for Basic Information Screenshot of the Overview webpage for an earthquake in Alaska. Clicking on the card will take the user to the Aftershock Forecast. People can find the Aftershock Forecast for a specific earthquake by starting at the Overview (default) webpage for that earthquake and selecting the “card” titled “Aftershock Forecast.” This card will only appear if an aftershock forecast was computed for that event. The time that the current forecast was released, and the planned time of the next forecast update, are included in each forecast. We update at least once within the first day, again within the first week, and again within the first month. We also update the forecasts over time to incorporate more information about the specific behavior of the aftershock sequence. Therefore, the forecasts are updated to keep current with the changing aftershock rate. The rate of aftershocks changes with time, generally decreasing, although sometimes temporarily increasing after a significant aftershock. We will not usually compute aftershock forecasts for earthquakes that are themselves aftershocks of a prior larger earthquake, or for earthquakes that occur as part of volcanic activity.įorecasts are updated regularly. We also compute forecasts for some smaller earthquakes that are of particular public interest, for example earthquakes in densely-populated areas. There are higher thresholds of M6 or 6.5 in some remote and poorly-instrumented areas. As an aftershock sequence progresses, our forecast also incorporates information about the behavior of that specific sequence.įorecasts are posted for earthquakes of M5+ in the United States and U.S. We use the behavior of past aftershock sequences to forecast the likelihood of future aftershocks. We forecast aftershock activity over future time intervals of a day,Ī week, a month, and a year. ![]()
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