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Site layout map showing seismicity (M W ≥ 5.5) of entire Aleutian arc and Alaska Peninsula. Solid cutting lines are lines of cross sections through Aleutian arc shown in Figs. 2-5.
Source publication
The tectonic position and overall geodynamic setting, as well as the seismological characteristics and peculiarities of the aftershock process, are considered for the source of the strongest Near Aleutian earthquake of July 17, 2017, МW = 7.8, on the Commander Islands. It is shown that in contrast to the eastern segments of the Aleutian island arc,...
Contexts in source publication
Context 1
... the arc ( Balakina and Moskvina, 2010). This also concerns the phenomenon of the subduction of the Pacific plate beneath the Aleutian island arc and beneath the Bering lithospheric plate along different segments of the Aleutian arc. The situation map of the M W ≥ 5.5 seismicity within the entire Aleutian arc and the Alaska Peninsula is shown in Fig. ...
Context 2
... 36 aftershocks with mb ≥ 4.2 were recorded during the first 6.5 days. Figure 10 shows a scheme of the foreshocks and aftershocks of the earthquake of July 17 for the period from July 17 to 20 inclusive, i.e., three days after the main event. By March 2018, the aftershock process appeared to be almost finished. ...
Context 3
... can be seen that the region of the first-three-day aftershocks (Fig. 10), tracing the source of the earthquakes of July 17, stretches from the Near Islands of the Aleutian Arc in the southeast to Bering Island's tip closest to Kamchatka in the northwest. B e r i n g I s l a n d B e r i n g I s l a n d B e r i n g I s l a n d M e d n y i I s la n d M e d n y i I s la n d M e d n y i I s la n d A l e u t i a ...
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... conversion from M W to M 0 is conducted by the Kanamori formula (Kanamori, 1978) Figure 11 shows the time behavior of the release of the cumulative scalar seismic moment M 0cum in the source (aftershock) area of the earthquake of July 17, 2017 from 1920 to 2017. The straight line is a linear regression approximating the observed data on the interval from 1924 to 1998 inclusive. ...
Context 5
... the end of February 2018, 83 aftershocks with mb ≥ 4.3 were detected according to the UMS catalog and 559 aftershocks with K S ≥ 8.3 (М W ≥ 1.9) were recorded according to RCKE. Figure 12 shows the time history of the release of M 0cum /M 0me in the aftershocks of the earthquake of July 17 in fractions of M 0 of the main event for the period from July 17, 2017 to February 27, 2018 inclusive. The graph is based on the RCKE data and CMT catalog. ...
Context 6
... difference between the regression line and the actually observed M 0cum time series approximately corresponds to the moment magnitude of the aftershock of January 25 means that the quasi-stationary phase of the M 0cum release in the aftershocks lasted about half-a-year. The period from August 3, 2017 to January 24, 2018 (from day 18 to day 186 in Fig. 12) can be considered as the phase of seismic quiescence within the aftershock sequence before the strong aftershock of January 25, ...
Context 7
... to the Central segment of the Aleutian Arc (the Rat and Andreanof islands) where the strongest earthquakes with M W 8. 6 (1957) and 8.7 (1965) occurred in the XX century, the western segment (the Commander and the Near islands) was not hit by the earthquakes with M W > 7.8 at least during the past 250 years. Moreover, these segments markedly differ in their internal structure: in the region of the Rat and Adreanof islands, there is a clearly pronounced seismic focal zone penetrating into the Earth almost down to the bottom of the intermediate depths (Figs. 1, 2), which suggests the existence of the subduction process there. Between the Commander and Near Islands, the phenomenon of the subduction ceases to exist so that beneath the Commander Islands, only the lithospheric seismicity really exists with the maximum of the hypocentral depth distribution at 10-50 km and a rapid decrease of the number of hypocenters at large depths. ...
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Large, destructive historical earthquakes off the coast of China’s Fujian Province point to important tectonic activity in the western Taiwan Strait that, until recently, has received little attention. We present newly acquired reflection seismic data that is used to study the shallow crustal structure of the western Taiwan Strait. With these data...
Citations
... All the previous studies of the NIAE focal mechanism show that the earthquake resulted in almost pure right-lateral strike-slip faulting along the Bering fault. In Rogozhin et al., 2019) it is stated that the NIAE seismic source in the form of a linear ~400 km long narrow zone practically completely occupied the northern slope of the Commander Island uplift and was located in the Bering fault zone. ...
A new model of the rupture surface of the Mw = 7.8 Near Islands Aleutian earthquake that occurred
on July 17, 2017 in the region of the Commander Islands of the Aleutian Island Arc is presented. The model
is based on the displacement fields obtained from Sentinel-1B radar images for the Bering and Mednyi
Islands. Among the interferogram pairs calculated from the images covering the period from June 17 to
August 28, 2017, the most reliable displacement fields were obtained from the image pair July 11–July 23,
2017. These displacements include coseismic and part of postseismic displacements. The inversion also
involved the displacement data recorded by the GNSS GPS stations on the Kamchatka Peninsula, Commander
Islands, and the closest to the epicenter Aleutian Islands. Due to the fact that displacements substantially
exceeding the noise level were only recorded at two GPS stations on the Bering and Shemya islands, the
use of the InSAR data substantially refines the existing earthquake source models. In our models, a seismic
rupture zone is approximated by a plane with a length of 370 km along the strike and 19 km along the dip,
respectively. Three models have been calculated: a model of uniform displacement across the entire rupture
surface; a model in which the rupture surface is divided strikewise into five elements; and a model divided
into four elements along the strike and into two levels along the dip, with a total of eight elements. All models
demonstrate the same displacement type—right-lateral strike-slip faulting with a relatively small thrust component.
According to the constructed models, the displacements in some areas of the rupture surface are
slightly smaller than average but, generally, they occur all over the source zone. The models based on satellite
geodetic data and on waveform inversion largely agree. The discrepancy between the models utilizing different
data types can probably be due to the fact that seismological data characterize the part of the source process
that is accompanied by the generation of seismic waves. Surface displacements estimated from InSAR
data do not characterize the main event alone but also contain contributions that may reflect various creep
processes. The period covered by the radar images also includes the foreshocks with magnitudes up to 6.3 as
well as more than 100 aftershocks with magnitudes between 4 to 5.5. Perhaps that is why the displacements
obtained in our models are more uniformly distributed over the 370-km rupture surface than in the models
based on the waveform analysis.
