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Event parameters (from USGS) ¶
These are preliminary results and are subject to change without notice. Please check the USGS page for the latest official information.
|UTC Time||Tuesday January 23, 2018 at 09:31:42 UTC|
|Region||Gulf of Alaska|
|Distance||280km SE of Kodiak, Alaska|
|Details||USGS Executive summary page|
- IRIS Earthquake Sci, @IRIS_EPO
- Alaska Earthquake Center, @AKEarthquake
- Stephen Hicks, @seismo_steve
- Anthony Lomax, @ALomaxNet
- patton_cascadia, @patton_cascadia
- Jascha Polet, @CPPGeophysics
Videos & Animations ¶
[IRIS DMC GMV Product] Alaska view of the Ground Motion Visualization (LHZ,LHN,LHE)
M7.9 earthquake, GULF OF ALASKA
Miscellaneous Contributions ¶
M7.9 Alaskan Earthquake recorded in Nevada using the Raspberry Shake (4.5 Hz) and a 1 Hz geophone
[Jim O'Donnell, HHseismic] The M7.9 event was recorded on two sites recording with Raspberry Shake (RS) seismometers (Z component); One at Nevada State College (Henderson) and one in Boulder City, 11 Kms separation, see Figures 1and 1aa. The Boulder City site also had 4.5, 2.5 and 1.0 Hz geophones recording on a Sigma 4 recorder for comparison. The comparison is quite good as can be seen in the Time Series and the Amplitude Spectra below for the RS and 1 Hz geophone. The RS uses a standard 4.5 Hz geophone (29V/m/s) while the 1 Hz geophone has an output of 200V/m/s. For many years prior to the development of Broad Band seismometers, like the Guralp CMG-3T in ~1980, the 1 Hz geophone was a very popular sensor in recording earthquakes in the western US.
The RS uses an inverse filter, in real time, to extend the frequency response from 4.5 Hz (~0.2s) to 0.2 Hz (5s). The 5s (0.2 Hz) response was modified to a 20s (0.05 Hz) response with a digital inverse filter. Consequently all the sensors (geophones) had the same response which was extended to f=0.05 (20s). This works quite nicely if you can stay above the noise of the recorder/sensor. Both the programs used to process the data and apply the Inverse filters were: WinQuake (Larry Cochrane-Public Seismic Network) and Sigma 4 (John Giles- Seismic Source Company). The RS also comes with adequate software to enable you to output rough plots and mini-seed format for further analysis (http://www.raspberryshake.org).
IRIS DMC Event Page
The IRIS DMC event page for this event contains links to additional tools and data.
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- Generalized GMVs: post-TA ground motion visualizations [Newsletter Article: 2025-12-28 Vol. 22, Num. 2]
- DMC short course at 2018 IRIS Workshop [Newsletter Article: 2018-03-23 Vol. 20, Num. 1]