scholarly journals Deep Dehydration as a Plausible Mechanism of the 2013 Mw 8.3 Sea of Okhotsk Deep-Focus Earthquake

2021 ◽  
Vol 9 ◽  
Author(s):  
Hao Zhang ◽  
Suzan van der Lee ◽  
Craig R. Bina ◽  
Zengxi Ge
Keyword(s):  
Transition Zone ◽  
Sea Of Okhotsk ◽  
Oceanic Lithosphere ◽  
Dual Band ◽  
Deep Earthquake ◽  
Dehydration Reactions ◽  
Plausible Mechanism ◽  
Wave Trains ◽  
Deep Focus ◽  
Globally Distributed

The rupture mechanisms of deep-focus (>300 km) earthquakes in subducting slabs of oceanic lithosphere are not well understood and different from brittle failure associated with shallow (<70 km) earthquakes. Here, we argue that dehydration embrittlement, often invoked as a mechanism for intermediate-depth earthquakes, is a plausible alternative model for this deep earthquake. Our argument is based upon the orientation and size of the plane that ruptured during the deep, 2013 Mw 8.3 Sea of Okhotsk earthquake, its rupture velocity and radiation efficiency, as well as diverse evidence of water subducting as deep as the transition zone and below. The rupture process of this earthquake has been inferred from back-projecting dual-band seismograms recorded at hundreds of seismic stations in North America and Europe, as well as by fitting P-wave trains recorded at dozens of globally distributed stations. If our inferences are correct, the entirety of the subducting Pacific lithosphere cannot be completely dry at deep, transition-zone depths, and other deep-focus earthquakes may also be associated with deep dehydration reactions.

scholarly journals OKHOTSK-III EARTHQUAKE 24.05.2013 with Mwreg=8.3, I0=6 (Sea of Okhotsk)

2019 ◽  
pp. 377-396 ◽  
Author(s):  
A. Chebrova ◽  
Iskander Abubakirov ◽  
A. Gusev ◽  
S. Droznina ◽  
A. Lander
Keyword(s):  
Sea Of Okhotsk ◽  
Response Spectrum ◽  
Strong Motion ◽  
Eastern Coast ◽  
Depth Range ◽  
Deep Earthquake ◽  
Macroseismic Effect ◽  
The North ◽  
Deep Focus ◽  
Motion Characteristics

The strongest deep earthquake on May 24, 2013 (Mwreg=8.3) is discussed. It occurred under the Sea of Okhotsk at a depth of about 630 km. The instrumental hypocenter location reported by the KB GS RAS is φ=54.75N, λ=153.78E, h=630 km. Three magnitudes were obtained: local magnitude ML=7.8, code-wave magnitude Mc=7.6, moment magnitude Mwreg=8.3. The Okhotsk earthquake hypocenter is located on the northern part of the ancient slab, practically at the lower end of the seismogenic region. The earthquake caused significant co-seismic displacements at most GNSS observation points. The earthquake focal mecha-nisms solutions have been obtained by three ways. The solutions are very similar. The submeridial hollow falling nodal plane seems more preferable. For the deep quake of May 24, 2013, a series of aftershocks were registered. The aftershock process had three consistent stages with different decay character. The cloud of deep-focus aftershocks has the 400200 km size, with the 450–700 km depth range and is extended in the North–South direction. The aftershock process has the three-phase character and can be considered as a stream of seismic events decreasing in time with three successive stages with different attenuation modes. The change in attenuation modes is associated with strong aftershocks. The duration of the decaying after-shock process is ~ 280 days. The anomalous distribution of impact was observed for the earthquake: 1) a large range of macroseismic effect – quake was felt throughout the World; 2) in the territory of Kamchatka, maximum shakes and ground motions were observed at the points located on the eastern coast of Kamchat-ka, and at comparable northern and western distances macroseismic and instrumental intensities were lower. Despite the globality of the macroseismic effect, in the nearest settlements (Kamchatka region), the earth-quake was felt with intensity up to 5–6 and caused no damage. The May 24, 2013 earthquake produced many strong motion records. The ground motion characteristics such as peak amplitudes of motion, spectral shape and response spectrum were received using the records of the earthquake from Kamchatka network of digital accelerographs.

Electrical conductivity in the mantle transition zone beneath Eastern China derived from L1-Norm C-responses

2020 ◽  
Vol 221 (2) ◽  
pp. 1110-1124 ◽  
Author(s):  
Yanhui Zhang ◽  
Aihua Weng ◽  
Shiwen Li ◽  
Yue Yang ◽  
Yu Tang ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Objective Function ◽  
Water Content ◽  
Transition Zone ◽  
Regularization Parameter ◽  
Eastern China ◽  
Bfgs Method ◽  
L1 Norm ◽  
Mantle Transition Zone ◽  
Dehydration Reactions

SUMMARY Constraining the distribution of water in different regions of the mantle remains one of the significant challenges to comprehend the global deep water cycle. Geomagnetic depth soundings can provide such constraint through the electrical conductivity structure. Hence, this study aims to propose a regularization technique that can estimate previously unavailable C-response. In the method, the objective function comprised an L1-norm measured data prediction error and a spectral smoothness constraint term. We used the data error of C-response to weight the predicted error. The L-BFGS method was introduced to determine the minimum point of the objective function, and the regularization parameter decreased adaptively during inversion. Thus, the geomagnetic data processed yielded high-quality C-responses in 31 stations in Eastern China. In addition, we obtained 1-D electrical conductivity profiles in the mantle transition zone (MTZ) beneath Eastern China from C-responses using the L-BFGS method. Compared with the global 1-D model, the conductivity–depth profiles revealed that the MTZ beneath Eastern China is more conductive in the east but more resistive in the west. The conversion of these conductivities to water content based on the mineral physics suggested that the MTZ beneath Eastern China is characterized by a high water concentration, approximately 0.2 and 1 wt per cent in the upper and lower MTZ, respectively. Owing to the inclusion of more stations, the water-rich region could be constrained roughly to the east of the North–South Gravity Lineament (NSGL). Further considering seismic images in the same area, this water content distribution pattern suggested that the front of the stagnant Pacific Plate in the lower MTZ might have reached the NSGL. However, the dehydration reactions in the stagnant slab were more active in the eastern part. Perhaps, some of these fluids migrated into the upper MTZ and could be the source of the trapped water found in the xenoliths from the deep upper mantle beneath Eastern China.

scholarly journals Intraplate volcanism triggered by bursts in slab flux

2020 ◽  
Vol 6 (51) ◽  
pp. eabd0953
Author(s):  
Ben R. Mather ◽  
R. Dietmar Müller ◽  
Maria Seton ◽  
Saskia Ruttor ◽  
Oliver Nebel ◽  
...  
Keyword(s):  
Transition Zone ◽  
Plate Tectonics ◽  
Isotope Geochemistry ◽  
Plate Boundary ◽  
Oceanic Lithosphere ◽  
Mantle Transition Zone ◽  
Age Progression ◽  
Intraplate Volcanism ◽  
Enriched Mantle ◽  
Eastern Australia

Long-lived, widespread intraplate volcanism without age progression is one of the most controversial features of plate tectonics. Previously proposed edge-driven convection, asthenospheric shear, and lithospheric detachment fail to explain the ~5000-km-wide intraplate volcanic province from eastern Australia to Zealandia. We model the subducted slab volume over 100 million years and find that slab flux drives volcanic eruption frequency, indicating stimulation of an enriched mantle transition zone reservoir. Volcanic isotope geochemistry allows us to distinguish a high-μ (HIMU) reservoir [>1 billion years (Ga) old] in the slab-poor south, from a northern EM1/EM2 reservoir, reflecting a more recent voluminous influx of oceanic lithosphere into the mantle transition zone. We provide a unified theory linking plate boundary and slab volume reconstructions to upper mantle reservoirs and intraplate volcano geochemistry.

The possibility of tsunami in the Sea of Okhotsk caused by deep-focus earthquakes

2016 ◽  
Vol 52 (2) ◽  
pp. 217-224 ◽  
Author(s):  
A. I. Zaytsev ◽  
E. N. Pelinovsky ◽  
A. A. Kurkin ◽  
I. S. Kostenko ◽  
A. Yalciner
Keyword(s):  
Sea Of Okhotsk ◽  
The Sea Of Okhotsk ◽  
Deep Focus

scholarly journals Okhotsk deep earthquake 24.05.2013: nature of coseismal earth’s oscillations and estimation of P-wave amplitudes at teleseismic distances

2019 ◽  
Vol 486 (2) ◽  
pp. 237-242
Author(s):  
I. P. Kuzin ◽  
L. I. Lobkovskiy ◽  
K. A. Dozorova
Keyword(s):  
Sea Of Okhotsk ◽  
Seismic Waves ◽  
P Wave ◽  
P Waves ◽  
Deep Earthquake ◽  
Epicentral Area ◽  
Seismic Stations ◽  
The Sea Of Okhotsk ◽  
Gps Observations

The results of coseismic GPS observations in the epicentral area of 2013 Sea-of- Okhotsk earthquake are presented and specific features of seismic waves amplitudes variations with distance are detected basing on the records of Russian and international seismic stations. Global propagation of P-waves for the Sea-of-Okhotsk and Bolivian (09.06.1994) earthquakes was studied and their amplitudes on teleseismic distances were estimated.

Partial melting of stagnant oceanic lithosphere in the mantle transition zone and its geophysical implications

Lithos ◽  
2017 ◽  
Vol 292-293 ◽  
pp. 379-387 ◽  
Author(s):  
Yanfei Zhang ◽  
Chao Wang ◽  
Zhenmin Jin ◽  
Lüyun Zhu
Keyword(s):  
Partial Melting ◽  
Transition Zone ◽  
Oceanic Lithosphere ◽  
Mantle Transition Zone
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