Fractal Dimension and b Value Mapping Before and After the 2004 Megathrust Earthquake in the Andaman-Sumatra Subduction Zone

2012 ◽  
pp. 55-62
Author(s):  
Sohini Roy ◽  
Uma Ghosh ◽  
Sugata Hazra ◽  
J. R. Kayal
Keyword(s):  
Fractal Dimension ◽  
Subduction Zone ◽  
B Value ◽  
Megathrust Earthquake ◽  
Before And After

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

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.

The two behaviours of Mt. Etna Volcano before and after a large intrusive episode: Evidences frombvalue and fractal dimension of seismicity

2001 ◽  
Vol 28 (11) ◽  
pp. 2257-2260 ◽  
Author(s):  
Sergio Vinciguerra ◽  
Stefano Gresta ◽  
Maria Serafina Barbano ◽  
Giovanni Distefano
Keyword(s):  
Fractal Dimension ◽  
Etna Volcano ◽  
Before And After ◽  
Mt Etna

scholarly journals Fractal Characterization of Earthquake occurrences in Nigeria

2019 ◽  
Vol 1 ◽  
pp. 281-287
Author(s):  
N N Abdulsalam ◽  
O Ologe
Keyword(s):  
Fractal Dimension ◽  
Active Zone ◽  
Hazard Analysis ◽  
B Value ◽  
Google Earth ◽  
Counting Method ◽  
Microsoft Word ◽  
Box Counting ◽  
Box Counting Method

Fractal characterization of Earthquake occurrences in Nigeria was carried out in order to know the b-value of tremor occurrences in the country. This will help in hazard analysis and research in the geological and geophysical structures of Nigeria. The method used in determining the b-value is the box counting method, but for simplicity, we used circle. The areas that are tremor prone were posted on a digitized Nigeria map using Google earth and Surfer 7.0 software. The computation with the box counting method was performed with picked radius of the circle from 50km - 350km and the average number of points that falls within each circle were recorded. The graph of log r (the logarithms of radius of circle or scale) against log <N> (logarithms of average number of points) was plotted using grapher and excels Microsoft word and the slope of the graph was determined. The determined slope gave the fractal dimension and the b-value was thus calculated. In this work, a b-value of 0.6 was obtained indicating that Nigeria falls within seismically less active zone.

scholarly journals Strong foreshock signal preceding the L'Aquila (Italy) earthquake (<i>M</i><sub>w</sub> 6.3) of 6 April 2009

2010 ◽  
Vol 10 (1) ◽  
pp. 19-24 ◽  
Author(s):  
G. A. Papadopoulos ◽  
M. Charalampakis ◽  
A. Fokaefs ◽  
G. Minadakis
Keyword(s):  
Hanging Wall ◽  
B Value ◽  
Aftershock Sequence ◽  
Earthquake Catalogue ◽  
Seismicity Rate ◽  
Background Seismicity ◽  
Before And After ◽  
Spatially Distributed ◽  
Drastic Increase ◽  
Seismogenic Area

Abstract. We used the earthquake catalogue of INGV extending from 1 January 2006 to 30 June 2009 to detect significant changes before and after the 6 April 2009 L'Aquila mainshock (Mw=6.3) in the seismicity rate, r (events/day), and in b-value. The statistical z-test and Utsu-test were applied to identify significant changes. From the beginning of 2006 up to the end of October 2008 the activity was relatively stable and remained in the state of background seismicity (r=1.14, b=1.09). From 28 October 2008 up to 26 March 2009, r increased significantly to 2.52 indicating weak foreshock sequence; the b-value did not changed significantly. The weak foreshock sequence was spatially distributed within the entire seismogenic area. In the last 10 days before the mainshock, strong foreshock signal became evident in space (dense epicenter concentration in the hanging-wall of the Paganica fault), in time (drastic increase of r to 21.70 events/day) and in size (b-value dropped significantly to 0.68). The significantly high seismicity rate and the low b-value in the entire foreshock sequence make a substantial difference from the background seismicity. Also, the b-value of the strong foreshock stage (last 10 days before mainshock) was significantly lower than that in the aftershock sequence. Our results indicate the important value of the foreshock sequences for the prediction of the mainshock.

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