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Data Event Response to the 27 July 2015 Mw 6.9 Earthquake 73km SW of Nikolski, Alaska

Written by David Phillips & Beth Bartel
27 July 2015

Tectonic Summary

From the USGS Event Page:
52.443°N 169.597°W depth=27.1 km (16.8 mi)

The Aleutian arc extends approximately 3,000 km from the Gulf of Alaska in the east to the Kamchatka Peninsula in the west. It marks the region where the Pacific plate subducts into the mantle beneath the North America plate. This subduction is responsible for the generation of the Aleutian Islands and the deep offshore Aleutian Trench.

Most of the seismicity along the Aleutian arc results from thrust faulting that occurs along the interface between the Pacific and North America plates, extending from near the base of the trench to depths of 40 to 60 km. Slip along this interface is responsible for generating devastating earthquakes. Deformation also occurs within the subducting slab in the form of intermediate-depth earthquakes that can reach depths of 250 km. Normal faulting events occur in the outer rise region of the Aleutian arc resulting from the bending of the oceanic Pacific plate as it enters the Aleutian trench. Additionally, deformation of the overriding North America plate generates shallow crustal earthquakes.

For more information, see the USGS Earthquake Hazards Program event page.

UNAVCO Response

In response to the Mw 6.9 earthquake 73km southwest of Nikolski, Alaska on July 27, 2015, one-sample-per-second (1-sps) GPS data are being collected for a 7-day period around the event (day of event ± 3 days). Once downloaded, data will be available from ftp://data-out.unavco.org/pub/highrate/.

Sites being downloaded and their horizontal distances to the epicenter:
AB02, 77.21 km (nearest site)
AB01, 315.09 km
AV09, 259.18 km
AV06, 318.18 km
AV07, 304.82 km
AV08, 303.56 km
AV10, 306.01 km
AV12, 315.38 km
AV13, 311.53 km
AV14, 312.30 km
AV15, 318.22 km

The GAGE GPS Analysis Center Coordinator will estimate coseismic offsets for any stations that experience horizontal displacements of > 1mm. If such offsets are observed, station offset files will be made available from ftp://data-out.unavco.org/pub/products/event/.

UNAVCO is also producing a fully processed 1-sps borehole strainmeter (BSM) dataset spanning the time period of this event, made available at http://borehole.unavco.org/bsm/earthquakes/20150727_Alaska/.

UNAVCO Data and Support

  • Please contact archive-gpsunavco.org for information on data availability

Related Links

Map Center:
Nikolski, Alaska


Last modified: 2020-02-06  00:23:17  America/Denver