scholarly journals Magmatic processes in the Alaska subduction zone by combined 3-D b value imaging and targeted seismic tomography

2009 ◽  
Vol 114 (B11) ◽  
Author(s):  
T. van Stiphout ◽  
E. Kissling ◽  
S. Wiemer ◽  
N. Ruppert
Keyword(s):  
Subduction Zone ◽  
Seismic Tomography ◽  
B Value ◽  
Magmatic Processes

Fractal dimension and b-value mapping in the Andaman-Sumatra subduction zone

2010 ◽  
Vol 57 (1) ◽  
pp. 27-37 ◽  
Author(s):  
Sohini Roy ◽  
Uma Ghosh ◽  
Sugata Hazra ◽  
J. R. Kayal
Keyword(s):  
Fractal Dimension ◽  
Subduction Zone ◽  
B Value

Seismic gaps and recurrence periods of large earthquakes along the Mexican subduction zone: A reexamination

1981 ◽  
Vol 71 (3) ◽  
pp. 827-843 ◽  
Author(s):  
S. K. Singh ◽  
L. Astiz ◽  
J. Havskov
Keyword(s):  
Subduction Zone ◽  
Risk Estimation ◽  
Source Parameters ◽  
Seismic Energy ◽  
B Value ◽  
Dislocation Model ◽  
Past Century ◽  
Seismic Gaps ◽  
Large Earthquakes ◽  
Mexican Subduction Zone

abstract Seismic gaps and recurrence periods of large, shallow interplate earthquakes along the Mexican subduction zone are reexamined after combining information from a catalog of nineteenth century's earthquakes, some relocated epicenters of the early part of this century, source parameters of recent large earthquakes, and redetermined magnitudes of great, shallow earthquakes of this century. Tehuantepec and Michoacan gaps have not experienced a large shock in this century and perhaps none in the past century; they are either aseismic or have anomalously large repeat times. Guerrero, Jalisco, and Ometepec regions presently appear to have a high seismic potential. Observed average repeat times of large earthquakes (Ms ≳ 7.4) in six regions (east, central, and west Oaxaca, San Marcos, Petatlan, and Colima) are between 32 to 56 yr. Data of this century indicate that the strain is released mostly in large events (Ms ≳ 7.4). A simple dislocation model with parameters obtained from the studies of recent earthquakes explains the observed recurrence periods quite well. The b value for this zone is not meaningful, an observation which is of significance for seismic risk estimation. Most of seismic moment (or, equivalently, seismic energy) release since 1800 appears to occur for 15 yr followed by relative quiescence in the next 15 yr.

Chromite and PGE geochemistry of the Elekdağ Ophiolite (Kastamonu, Northern Turkey): Implications for deep magmatic processes in a supra-subduction zone setting

2014 ◽  
Vol 57 ◽  
pp. 216-228 ◽  
Author(s):  
Cahit Dönmez ◽  
Serdar Keskin ◽  
Kurtuluş Günay ◽  
Aydın Olcay Çolakoğlu ◽  
Yahya Çiftçi ◽  
...  
Keyword(s):  
Subduction Zone ◽  
Magmatic Processes ◽  
Pge Geochemistry

scholarly journals Gutenberg-Richter b value studies along the Mexican Subduction Zone and data constraints

2020 ◽  
Vol 59 (4) ◽  
pp. 285-298
Author(s):  
Lenin Ávila-Barrientos ◽  
F. Alejandro Nava Pichardo
Keyword(s):  
Seismic Hazard ◽  
Subduction Zone ◽  
B Value ◽  
Seismicity Rates ◽  
Magnitude Scales ◽  
Data Constraints ◽  
Large Earthquakes ◽  
Adequate Data ◽  
Seismic Catalog ◽  
Mexican Subduction Zone

The Gutenberg-Richter b value is one of the most important tools for seismic hazard studies; this value is most useful in estimating seismicity rates, and also is related to ambient stress levels and shows changes precursory to the occurrence of large earthquakes. However, correct and reliable determinations of the b value are critically dependent on having adequate data samples. Studies oriented to corroborate whether precursory changes in the b value occur before large (M ? 7.0) along the Mexican subduction zone, were done based on data from the Servicio Sismológico Nacional (SSN, Mexico’s National Seismological Service) seismic catalog, from 1988 to 2018. Results for five earthquakes are suggestive that precursory changes may occur, but differences between measured values are not significant because of large uncertainties due to the SSN using different magnitude scales for small (below M ~4.5) and medium to large (above M ~4.5) magnitudes. We submit that until an appropriate scale is implemented for small magnitudes, results from b-value studies based on SSN data should be considered critically.

Spatiotemporal Seismotectonic Implications for the Izu–Bonin–Mariana Subduction Zone from b-Values

2020 ◽  
Vol 91 (3) ◽  
pp. 1679-1693
Author(s):  
Zhou Gui ◽  
Yongliang Bai ◽  
Zhenjie Wang ◽  
Dongdong Dong ◽  
Shiguo Wu ◽  
...  
Keyword(s):  
Subduction Zone ◽  
Cross Sections ◽  
Local Stress ◽  
B Value ◽  
Seismic Risk Analysis ◽  
B Values ◽  
Magnitude Distribution ◽  
Before And After ◽  
Earthquake Potential ◽  
Metastable Olivine

Abstract Studies on the physical properties of the entire Izu–Bonin–Mariana (IBM) subduction zone contribute to comprehensive seismotectonic understanding and earthquake potential assessment, especially given previous controversial conclusions. Determining seismic b-value is a method that has been used for other regions and is adopted here to study the spatiotemporal variations along the IBM system. Based on the frequency–magnitude distribution relation log10(N)=a−bM, b-values are mapped within the subduction zone using earthquakes with Mw≥2 after 2005. The b-value anomalies in cross sections indicate detailed seismotectonic characteristics against the regional geological background. The common characteristics from north to south: (1) regional high b-values at shallow depths in the overriding are associated with relatively low temperatures in thermal model, the bottom half of which correspond with highly serpentinized mantle wedge; and (2) low b-values at intermediate depths are associated with high temperatures along the primarily heated hydrated slab. In the Izu–Bonin segment, low b-values around the slab deflection at deep depths respond to stress buildup and shearing instability of metastable olivine in primarily heated hydrated slabs. In the Mariana segment, high b-values beneath the volcanic region at depths from the surface to 50 km and between 50 and 100 km are associated with extension and volcanism and the melting region, respectively. Temporal b-value variations indicate regional changes before and after large events for further seismic risk analysis. Stress drops of large intermediate and deep earthquakes are negligible to local stress state in strong flexure of the incoming slab. The rupture zone around the Pagan region at an approximate depth of 200 km and the region around the rifting–spreading transition in the northern Mariana trough at depths between 180 and 350 km are areas for potential large earthquakes.

Seismicity time evolution and 3D/4D seismic tomography of Nesjavellir geothermal field (Iceland)

2020 ◽  
Author(s):  
Ortensia Amoroso ◽  
Ferdinando Napolitano ◽  
Vincenzo Convertito ◽  
Raffaella De Matteis ◽  
Paolo Capuano
Keyword(s):  
Power Plant ◽  
Seismic Tomography ◽  
Geothermal Energy ◽  
Clean Energy ◽  
Velocity Model ◽  
B Value ◽  
Geothermal Field ◽  
Hot Water ◽  
Central Volcano ◽  
4D Seismic

<p>Nesjavellir Geothermal Field is located in the Northern part of the Hengill central volcano in South West Iceland. The Hengill volcanic complex consists of three smaller volcanic systems feeding several geothermal fields with surface manifestations.</p><p>Geothermal energy is currently produced at two power plants, in Nesjavellir and in Hellisheidi. After an exploitation period started in 1947, the construction of Nesjaveillir power plant was completed in 1990. Nowadays it produces geothermal energy of up to 300 MW, which is 1,640 l/sec of hot water and up to 120 MW of electricity.</p><p>Part of the surplus geothermal water from the plant goes into the injection wells and in analogy with the nearby Hellisheidi power plant the re-injection of geothermal gases into basaltic formations is planned. To this aim several tests of fluids deep injection are being conducted to prepare the experimental re-injection of carbon dioxide and hydrogen sulphide.</p><p>In the framework of the H2020-Science4CleanEnergy project, S4CE, a multi-disciplinary project aimed at understanding the underlying physical mechanisms underpinning sub-surface geo-energy operations and to measure, control and mitigate their environmental risks, we investigate the seismicity evolution through the b-value and study the elastic properties of the propagation medium through the 3D/4D seismic tomography.</p><p>The seismicity recorded in the study area is due to different mechanisms. Indeed, while in Hengill the seismicity is originated by volcano-tectonic processes, small earthquake swarms between Hengill and Grensdalur volcano are due to the geothermal activity. Finally, the seismicity in proximity of Hellishedi and Nesjaveiilir power plant appears to be induced by re-injection of waste water from the geothermal production.</p><p>Seismic data are recorded by the Icelandic Meteorological Office (IMO) but also from Iceland GeoSurvey (ÍSOR) and by the COSEISMIQ project. The production data are from the OR energy company.</p><p>We used an iterative linearized delay-time inversion to estimate both the 3D P and S velocity models and earthquake locations. The velocity model is parametrized by trilinear interpolation on a 3D grid. The inversion starts from the 1D velocity model, optimized for the area. Time variations of the medium seismic properties are observed in term of Vp, Vs and Vp/Vs ratio obtained by 4D tomography. The technique consists in applying the 3D tomography at consecutive epochs. Spatial and temporal characteristics of the re-located earthquakes are then analysed by using the ZMAP code to image the b-value in the investigate volume.</p><p>The images obtained for each epoch in terms of b-value, Vp and Vs velocities are then correlated with operational data.</p><p> </p><p>This work has been supported by S4CE ("Science for Clean Energy") project, funded from the European Union’s Horizon 2020 - R&I Framework Programme, under grant agreement No 764810 and by PRIN-2017 MATISSE project funded by Italian Ministry of Education and Research.</p>

Imaging b -value depth variations within the Cocos and Rivera plates at the Mexican subduction zone

2018 ◽  
Vol 734-735 ◽  
pp. 33-43 ◽  
Author(s):  
Quetzalcoatl Rodríguez-Pérez ◽  
F. Ramón Zuñiga
Keyword(s):  
Subduction Zone ◽  
B Value ◽  
Mexican Subduction Zone
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