Evaluation of global seismicity along Northern and Southern hemispheres

Abstract. An earthquake has been identified as one of the major natural disasters that cause loss of lives and property. To mitigate this disaster, knowledge of global seismicity is essential. This research is aimed at evaluating the Gutenberg Richter b-value parameter and focal depth distribution of earthquake parameters to identify the prominent earthquake-prone zones in the Northern and Southern hemispheres. The study area covers 20° to the Northern and Southern hemispheres, with the equator in the middle. The data were obtained from the earthquake catalogue of the Advanced National Seismic System (ANSS) hosted by the Northern California Earthquake Data Centre USA from 1963–2018. Fifty-four-year earthquake data of M ≥ 6.0 were processed and analyzed using Gutenberg-Richter (GR). The b-value parameters obtained from the GR model were plotted against the hemispheres using bar chart graphs to determine the tectonic stress level of the study region. The earthquake energy released was evaluated along the Northern and Southern hemispheres for a proper understanding of seismic events in the study region. It was observed that the rate of earthquake occurrence at the Southern hemisphere is higher than the Northern hemisphere. The b-values obtained in all the zones vary from 0.82–1.16. At the same time, the maximum earthquake energy of 4.6 × 1025 J was estimated. Low b-values indicate high tectonic stress within the plates. The large tectonic stress accumulation around the equator suggests that unstable lithospheres characterize this zone.

Download Full-text

Box Counting Fractal Dimension and Frequency Size Distributon of Earthquakes in the Central Himalaya Region

Journal of Institute of Science and Technology ◽

10.3126/jist.v26i2.41664 ◽

2021 ◽

Vol 26 (2) ◽

pp. 127-136

Author(s):

Ram Krishna Tiwari ◽

Harihar Paudyal

Keyword(s):

Fractal Dimension ◽

High Stress ◽

High Strength ◽

B Value ◽

Earthquake Catalog ◽

Central Himalaya ◽

Study Region ◽

B Values ◽

Box Counting ◽

Earthquake Distribution

To establish the relations between b-value and fractal dimension (D0) for the earthquake distribution, we study the regional variations of those parameters in the central Himalaya region. The earthquake catalog of 989 events (Mc = 4.0) from 1994.01.31 to 2020.10.28 was analyzed in the study. The study region is divided into two sub-regions (I) Region A: 27.3°N -30.3°N and 80°E -84.8°E (western Nepal and vicinity) and (II) Region B: 26.4°N -28.6°N and 84.8°E -88.4°E (eastern Nepal and vicinity). The b-value observed is within the range between 0.92 to 1.02 for region A and 0.64 to 0.74 for region B showing the homogeneous nature of the variation. The seismic a-value for those regions ranges respectively between 5.385 to 6.007 and 4.565 to 5.218. The low b-values and low seismicity noted for region B may be related with less heterogeneity and high strength in the crust. The high seismicity with average b-values obtained for region A may be related with high heterogeneity and low strength in the crust. The fractal dimension ≥1.74 for region A and ≥ 1.82 for region B indicate that the earthquakes were distributed over two-dimensional embedding space. The observed correlation between D0 and b is negative for western Nepal and positive for eastern Nepal while the correlation between D0 and a/b value is just opposite for the respective regions. The findings identify both regions as high-stress regions. The results coming from the study agree with the results of the preceding works and reveal information about the local disparity of stress and change in tectonic complexity in the central Himalaya region.

Download Full-text

The Reliance of the Earthquake B-Value on Depth and Focal Mechanism

Iraqi Geological Journal ◽

10.46717/igj.54.1d.1ms-2021-04-21 ◽

2021 ◽

Vol 54 (1D) ◽

pp. 1-10

Author(s):

Emad Al-Heety

Keyword(s):

Moment Tensor ◽

Focal Depth ◽

Seismic Hazard Assessment ◽

B Value ◽

Strike Slip ◽

Focal Mechanisms ◽

Likelihood Method ◽

Centroid Moment Tensor ◽

B Values ◽

Completeness Magnitude

The earthquake size distribution (b-value) is a significant factor to recognize the seismic activity, seismotectonic, and seismic hazard assessment. In the current work, the connection of the b-constant value with the focal depth and mechanism was studied. The effect of the study scale (global, regional and local) on the dependence of b-value on the focal mechanisms was investigated. The database is quoted from the Global Centroid Moment Tensor catalog. The selected earthquakes are the shallow normal, reverse and strike-slip events. The completeness magnitude (Mc) is 5.3. The maximum likelihood method is utilized to compute the b-value. The obtained results show that the b-value is decreasing with depth to range 10-20 km, then increases to the depth of 40km. The turning point of b-value (increasing of b-value) locates at the depth of the transition brittle-ductile zone. Globally and regionally, low, moderate, and high b-values are associated with reverse, strike-slip, and normal focal mechanisms, respectively, while locally, the relation between b-values and focal mechanisms shows different association trends, such as low, moderate, and high b-values are associated with normal, strike-slip, and reverse focal mechanisms and so on.

Download Full-text

Spatial Variation of b-Values and Their Relationship with the Fault Blocks in the Western Part of the Tibetan Plateau and Its Surrounding Areas

Entropy ◽

10.3390/e22091016 ◽

2020 ◽

Vol 22 (9) ◽

pp. 1016

Author(s):

Hamid Hussain ◽

Zhang Shuangxi ◽

Muhammad Usman ◽

Muhammad Abid

Keyword(s):

Tibetan Plateau ◽

B Value ◽

Strike Slip ◽

The Tibetan Plateau ◽

Gorkha Earthquake ◽

Study Region ◽

B Values ◽

Fractured Medium ◽

Surrounding Areas ◽

Near Future

The Tibetan Plateau is considered to be one of the best natural laboratories for seismological research. This study sought to determine the spatial variations of b-values in the western part of the Tibetan Plateau, along with its surrounding areas, and the relation with the region’s fault blocks. The study region lies within 27–36.5° N, 78–89° E, and its fracture structure consists of strike-slip faults, as well as normal and thrust faults. A catalog record from 2009–2019 provided 4431 well-centered earthquakes that varied in magnitude from 0.1 to 8.2 M. The record was obtained from China’s seismological network, which is capable of recording low magnitudes to analyze b-values in the study area. The key findings of this study are as follows: (1) the range of earthquake depth in the region was 0–256 km, with the depth histogram showing a high frequency occurrence of shallow earthquakes in the area; (2) a time histogram showed that the major earthquakes occurred between 2014–2015, including the notable 2015 Gorkha earthquake (M = 8.2); (3) the b-value computed in the study area was 0.5 to 1.6, but in most of the study area, the b-value ranged from 0.6 to 0.9, which was a low to intermediate value, due to the presence of strike-slip faults in the central part of the study area and underthrusting in the region (south of the study area); and (4) a high b-value was found in the northwestern and eastern regions of the area, which proved that the area is prone to small earthquakes in the near future. The study also showed that the central and southern areas of the study region had low to intermediate b-values, meaning that it is prone to destructive and massive earthquakes with high magnitudes, such as the Gorkha earthquake (southern part of the study area). Low b-values revealed the degree of variation in rock properties, including large stress and strain, a fractured medium, a high deformation rate, and large faults. Small b-values were observed when the stress level was high in the investigated region, which might be used to predict a massive high-magnitude earthquake in the near future.

Download Full-text

Determination of temporal value of a-value and b-value to identify the level brittle of rock and seismic activity in the Palu region

Journal of Physics Theories and Applications ◽

10.20961/jphystheor-appl.v3i1.39431 ◽

2019 ◽

Vol 3 (1) ◽

pp. 1

Author(s):

Afryanti Veronika Simangunsong ◽

Ramadhan Priadi ◽

Anak Agung Istri Dwilyantari ◽

Agus Marsono

Keyword(s):

Maximum Likelihood ◽

Seismic Activity ◽

B Value ◽

B Values ◽

A Value ◽

Calculation Results ◽

Resistance To Stress ◽

Index Value ◽

Earthquake Data

<span lang="EN-US">The Palu area is a region that has a high seismic potential as a result of the existence of the Palu Koro Fault. The Koro Palu Fault is an active sinistral fault that moves with velocity around 25-30 mm/year. This research purpose to determine the a-value and b-value temporally for identify rock brittle levels and seismicity levels in the Palu area using the Maximum Likelihood Guttenberg-Richter method. The data used in this study are earthquake data from the BMKG and USGS catalogs for 2008-2018 over a period of 10 years located at 0840 LU 40 2.620LS and 118,590 BT - 121.70 BT. Based on the results of data processing, there were 3033 earthquake distributions in the earthquake over a 10-year period. The calculation results show variations in the value of b-values in the range 0.55-0.961 and the a-value in the range 3.63-5.42. The highest b-value was obtained in 2015 at 0.961 as an indication of increased seismic activity in the Palu area. After the Palu M 7.4 earthquake on 28 September 2018, there was a significant decrease in the value of the b-value to 0.685. Based on the trend of b-value values which continued to decline from 2015 until 2018, it was identified in the rock's resistance to stress is high in the Palu area. Whereas for the seismicity index value of the Palu area of 0.040789 with the earthquake return period 7 is 25 years. </span>

Download Full-text

Statistical analysis of aftershock sequences related with two major Nepal earthquakes: April 25, 2015, MW 7.8, and May 12, 2015, MW 7.2

Annals of Geophysics ◽

10.4401/ag-7025 ◽

2016 ◽

Vol 59 (5) ◽

Author(s):

Prasanta Chingtham ◽

Babita Sharma ◽

Sumer Chopra ◽

Pareshnath SinghaRoy

Keyword(s):

Scaling Laws ◽

Main Shock ◽

B Value ◽

Temporal Variations ◽

Aftershock Sequence ◽

Earthquake Catalog ◽

Study Region ◽

Nepal Himalaya ◽

B Values ◽

Aftershock Sequences

Present study describes the statistical properties of aftershock sequences related with two major Nepal earthquakes (April 25, 2015, MW 7.8, and May 12, 2015, MW 7.2) and their correlations with the tectonics of Nepal Himalaya. The established empirical scaling laws such as the Gutenberg–Richter (GR) relation, the modified Omori law, and the fractal dimension for both the aftershock sequences of Nepal earthquakes have been investigated to assess the spatio-temporal characteristics of these sequences. For this purpose, the homogenized earthquake catalog in moment magnitude, MW is compiled from International Seismological Center (ISC) and Global Centroid Moment Tensor (GCMT) databases during the period from April 25 to October 31, 2015. The magnitude of completeness, MC, a and b-values of Gutenberg–Richter relationship for the first aftershock sequence are found to be 3.0, 4.74, 0.75 (±0.03) respectively whereas the MC, a and b-values of the same relationship for the second aftershock sequence are calculated to be 3.3, 5.46, 0.90 (±0.04) respectively. The observed low b-values for both the sequences, as compared to the global mean of 1.0 indicate the presence of high differential stress accumulations within the fractured rock mass of Nepal Himalaya. The calculated p-values of 1.01 ± 0.05 and 0.95 ± 0.04 respectively for both the aftershock sequences also imply that the aftershock sequence of first main-shock exhibits relatively faster temporal decay pattern than the aftershock sequence of second main-shock. The fractal dimensions, DC values of 1.84 ± 0.05 and 1.91 ± 0.05 respectively for both the aftershock sequences of Nepal earthquakes also reveal the clustering pattern of earthquakes and signifies that the aftershocks are scattered all around the two dimensional space of fractured fault systems of the Nepal region. The low b-value and low DC observed in the temporal variations of b-value and DC before the investigated earthquake (MW 7.2) suggest the presence of high-stress concentrations in the thrusting regimes of the Nepal region before the failure of faults. Moreover, the decrease of b-value with the corresponding decrease of DC observed in their temporal variations can primarily act as an indicator for possible prediction of major earthquakes in the study region.

Download Full-text

A Seismic Alert System for Oil & Gas Offshore Fields

10.2118/207296-ms ◽

2021 ◽

Author(s):

Pamela Poggi ◽

Emilia Fiorini ◽

Daniela Tonoli ◽

Francesca Ioele ◽

Eric John Parker ◽

...

Keyword(s):

Real Time ◽

Ground Motion ◽

Oil And Gas ◽

Focal Depth ◽

Threshold Values ◽

Alert System ◽

Ground Acceleration ◽

Gas Field ◽

Expected Values ◽

Earthquake Data

Abstract Objectives/Scope This paper presents an innovative web tool developed for the seismic monitoring of critical infrastructure. As an example, we describe an application for the ENI offshore facilities, Jangkrik and Merakes Fields Development, offshore Indonesia. Methods, Procedures, Process The system monitors reported seismic activity in a project area, and issues warnings when earthquakes detected may have directly or indirectly impacted facilities. Notifications allow the owner to optimize decisions regarding post-earthquake asset surveys and maintenance, avoiding the need for inspections in areas not significantly affected. A system of email alerts and a web based GIS platform provide the end-user with a tool to control its own assets. Results, Observations, Conclusions The purpose of the tool is to indirectly monitor earthquakes in an area and identify those which may have damaged the Oil and Gas facilities of interest. This identification requires accurate near real-time earthquake data such as date, time, location, magnitude, and focal depth. To this end, the system retrieves earthquake data from a qualified set of public seismic agencies. The system computes the expected values of shaking at the specific offshore facilities (platforms, subsea structures, pipelines, etc.). Calculations are based on sets of Ground Motion Prediction Equations (GMPEs) selected to match the seismotectonic environment. The expected values of seismic acceleration generated by an earthquake are compared with threshold values and a warning message is issued to the facilities supervisors when the ground acceleration exceeds design values. Threshold values related to secondary seismic effects (e.g., seismically induced landslides, debris flow) which could affect facilities integrity are also considered in the alert system. Threshold values are defined considering project seismic and geohazard documents, to summarize strong ground motion parameters that could potentially trigger damaging seismic geohazards, and project design documents to collect all data about seismic design of the assets. Monitoring intervals are defined based on the documentation screening. Several alarm levels are selected, based on the potential severity of earthquake effects. The more severe levels of ground motion, with high damage potential, can trigger recommendation for inspection. Novel/Additive Information Asset integrity and safety are key drivers in the offshore petroleum industry. Safety performance with respect to earthquakes is a fundamental issue in all seismic prone areas. The seismic alert system presented highlights, in near real time, earthquakes that are potentially critical for structures in an Oil and Gas field. This allows the owners to make quick decisions and plan necessary intervention regarding assets affected directly or indirectly by earthquakes. Exploiting the wide background of knowledge in engineering and geoscience and the modern availability of global earthquake data, the tool can provide useful assistance in managing asset integrity, regardless of the availability of local seismic networks or strong motion stations.

Download Full-text

Real-time seismology at UC Berkeley: The Rapid Earthquake Data Integration project

Bulletin of the Seismological Society of America ◽

10.1785/bssa0860040936 ◽

1996 ◽

Vol 86 (4) ◽

pp. 936-945 ◽

Cited By ~ 2

Author(s):

Lind S. Gee ◽

Douglas S. Neuhauser ◽

Douglas S. Dreger ◽

Michael E. Pasyanos ◽

Robert A. Uhrhammer ◽

...

Keyword(s):

Data Integration ◽

Strong Motion ◽

Seismic Network ◽

Prototype System ◽

Earthquake Parameters ◽

Moment Tensors ◽

Automatic Information ◽

Integration Project ◽

Earthquake Data

Abstract The Rapid Earthquake Data Integration project is a system for the fast determination of earthquake parameters in northern and central California based on data from the Berkeley Digital Seismic Network and the USGS Northern California Seismic Network. Program development started in 1993, and a prototype system began providing automatic information on earthquake location and magnitude in November of 1993 via commercial pagers and the Internet. Recent enhancements include the exchange of phase data with neighboring networks and the inauguration of processing for the determination of strong-motion parameters and seismic moment tensors.

Download Full-text

Earthquake sequences and b values in the southeast United States

Bulletin of the Seismological Society of America ◽

10.1785/bssa0640010267 ◽

1974 ◽

Vol 64 (1) ◽

pp. 267-273

Author(s):

Leland Timothy Long

Keyword(s):

United States ◽

South Carolina ◽

B Value ◽

Earthquake Activity ◽

Southeast United States ◽

B Values ◽

History Of ◽

Earthquake Sequences ◽

Foreshock Activity ◽

Epicentral Region

abstract Aftershock and foreshock activity within 12 hr of the July 13, 1971 earthquake near Seneca, South Carolina, indicates a b value of 0.9 at ML = 3.0. Approximately 40 events recorded in a 5-day aftershock survey near Seneca indicate a b value of 1.7 at ML = 0.5. A sequence of over 40 events occurring west of McCormick, South Carolina, indicates a b value of 1.3 at ML = 2.4. The McCormick sequence was active for 4 months. Unlike the Seneca region, the McCormick region has a history of earthquake activity. Examinations of other published southeastern b values suggest that southeastern United States earthquakes originate from conditions of ambient stress which vary with epicentral region or magnitude.

Download Full-text

Source Parameter of Earthquakes in Talala, Gujarat (India): An Implication towards Seismotectonic

Proceedings ◽

10.3390/iecg2019-06223 ◽

2019 ◽

Vol 24 (1) ◽

pp. 7

Author(s):

Sandeep Kumar Aggarwal

Keyword(s):

Epicentral Distance ◽

Moment Tensor ◽

Source Parameters ◽

Focal Depth ◽

B Value ◽

Complete Sequence ◽

P Value ◽

Centroid Moment Tensor ◽

North East ◽

Lateral Plane

Talala is an excellent example of triggered neo-tectonic seismicity between two dams during a monsoon. An earthquake of Mmax 5.1 on 6 November 2007 at 21.16° N; 70.54° E, with a focal depth of 4.5 km and complete sequence, was first-time recorded on the latest broadband sensor. This found a dam/monsoon-induced earthquake preceded by 18 foreshocks of 2 ≤ Mw ≤ 4.8 within 9 h 11 minute, as well as smaller shocks that may not have been recorded because of sparse network coverage. After the deployment of local mobile observatories, aftershocks of Mw ≥ 1.0, which continued for months and subsided to background seismicity after four months, were recorded. The same kind of phenomena repeated, with Mmax 5.0 on 20 October 2011 at 21.06° N; 70.50° E, focal depth 5.5 km, which implies that the potential to generate dam/monsoon-induced seismicity took nearly four years again. These phenomena continued and the sequence was recorded by a network of 10 broadband seismographs (three in the Talala area and seven at an epicentral distance of 30 to 300 km). Centroid Moment Tensor (CMT) solutions and spectral source parameters of mainshock and aftershocks are evaluated to understand the seismotectonic of the region. The CMT depicts a major strike-slip motion along East North East-West South West with a left-lateral plane at 4.5 km depth. This indicates a sympathetic fault extension of the Son-Narmada fault. The source parameters of 400 shocks of Mw 1.0 to 5.1 found seismic moment 1011 to 1016.5 N-m, source radii 120–850 meter, and a stress drop of 0.003 to 25.43 Mpa. The b-value, p-value, fractal dimension, and slip on estimated different faults. The comparison between Talala and Koyna dam-induced source parameters tries to establish a comparison of seismicity from different parts of the world.

Download Full-text

Two Foreshock Sequences Post Gulia and Wiemer (2019)

Seismological Research Letters ◽

10.1785/0220200082 ◽

2020 ◽

Vol 91 (5) ◽

pp. 2843-2850 ◽

Cited By ~ 3

Author(s):

Kelian Dascher-Cousineau ◽

Thorne Lay ◽

Emily E. Brodsky

Keyword(s):

Puerto Rico ◽

Real Time ◽

Exact Result ◽

Monte Carlo Sampling ◽

B Value ◽

Aftershock Sequence ◽

Traffic Light ◽

B Values ◽

Aftershock Sequences ◽

Abrupt Changes

Abstract Recognizing earthquakes as foreshocks in real time would provide a valuable forecasting capability. In a recent study, Gulia and Wiemer (2019) proposed a traffic-light system that relies on abrupt changes in b-values relative to background values. The approach utilizes high-resolution earthquake catalogs to monitor localized regions around the largest events and distinguish foreshock sequences (reduced b-values) from aftershock sequences (increased b-values). The recent well-recorded earthquake foreshock sequences in Ridgecrest, California, and Maria Antonia, Puerto Rico, provide an opportunity to test the procedure. For Ridgecrest, our b-value time series indicates an elevated risk of a larger impending earthquake during the Mw 6.4 foreshock sequence and provides an ambiguous identification of the onset of the Mw 7.1 aftershock sequence. However, the exact result depends strongly on expert judgment. Monte Carlo sampling across a range of reasonable decisions most often results in ambiguous warning levels. In the case of the Puerto Rico sequence, we record significant drops in b-value prior to and following the largest event (Mw 6.4) in the sequence. The b-value has still not returned to background levels (12 February 2020). The Ridgecrest sequence roughly conforms to expectations; the Puerto Rico sequence will only do so if a larger event occurs in the future with an ensuing b-value increase. Any real-time implementation of this approach will require dense instrumentation, consistent (versioned) low completeness catalogs, well-calibrated maps of regionalized background b-values, systematic real-time catalog production, and robust decision making about the event source volumes to analyze.

Download Full-text