Impact of magnitude uncertainties on seismic catalogue properties
Leptokaropoulos, K. M. ; Adamaki, A. K. LU
; Roberts, R. G.
; Gkarlaouni, C. G.
and Paradisopoulou, P. M.
(2018)
In Geophysical Journal International
213(2).
p.940-951
- Abstract
Catalogue-based studies are of central importance in seismological research, to investigate the temporal, spatial and size distribution of earthquakes in specified study areas. Methods for estimating the fundamental catalogue parameters like the Gutenberg-Richter (G-R) b-value and the completeness magnitude (Mc) are well established and routinely applied. However, the magnitudes reported in seismicity catalogues contain measurement uncertainties which may significantly distort the estimation of the derived parameters. In this study, we use numerical simulations of synthetic data sets to assess the reliability of different methods for determining b-value and Mc, assuming the G-R law validity. After contaminating the... (More)
Catalogue-based studies are of central importance in seismological research, to investigate the temporal, spatial and size distribution of earthquakes in specified study areas. Methods for estimating the fundamental catalogue parameters like the Gutenberg-Richter (G-R) b-value and the completeness magnitude (Mc) are well established and routinely applied. However, the magnitudes reported in seismicity catalogues contain measurement uncertainties which may significantly distort the estimation of the derived parameters. In this study, we use numerical simulations of synthetic data sets to assess the reliability of different methods for determining b-value and Mc, assuming the G-R law validity. After contaminating the synthetic catalogues with Gaussian noise (with selected standard deviations), the analysis is performed for numerous data sets of different sample size (N). The noise introduced to the data generally leads to a systematic overestimation of magnitudes close to and above Mc. This fact causes an increase of the average number of events above Mc, which in turn leads to an apparent decrease of the b-value. This may result to a significant overestimation of seismicity rate even well above the actual completeness level. The b-value can in general be reliably estimated even for relatively small data sets (N < 1000) when only magnitudes higher than the actual completeness level are used. Nevertheless, a correction of the total number of events belonging in each magnitude class (i.e. 0.1 unit) should be considered, to deal with the magnitude uncertainty effect. Because magnitude uncertainties (here with the form of Gaussian noise) are inevitable in all instrumental catalogues, this finding is fundamental for seismicity rate and seismic hazard assessment analyses. Also important is that for some data analyses significant bias cannot necessarily be avoided by choosing a high Mc value for analysis. In such cases, there may be a risk of severe miscalculation of seismicity rate regardless the selected magnitude threshold, unless possible bias is properly assessed.
(Less)
- author
- Leptokaropoulos, K. M.
; Adamaki, A. K.
LU
; Roberts, R. G.
; Gkarlaouni, C. G.
and Paradisopoulou, P. M.
- publishing date
- 2018-05-01
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- Numerical approximations and analysis, Statistical methods, Statistical seismology
- in
- Geophysical Journal International
- volume
- 213
- issue
- 2
- pages
- 12 pages
- publisher
- Oxford University Press
- external identifiers
-
- scopus:85044359254
- ISSN
- 0956-540X
- DOI
- 10.1093/gji/ggy023
- language
- English
- LU publication?
- no
- additional info
- Funding Information: This work was supported within SHEER: ‘SHale gas Exploration and Exploitation induced Risks’ project funded from the European Union Horizon 2020—Research and Innovation Programme, under grant agreement 640896. The work was also partially supported within statutory activities no. 3841/E-41/S/2017 of the Ministry of Science and Higher Education of Poland. AA acknowledges funding from the Jubilee scholarship (Uppsala University). The magnitude distribution parameters and the magnitude of completeness were estimated by MCCalc program, which can be downloaded from IS-EPOS: Induced Seismicity European Plate Observing System web platform https://tcs.ah-epos.eu/ after registration. The data used in this study can be found at http:// geophysics.geo.auth.gr/ss/station index en.html. Publisher Copyright: © The Author(s) 2018. Published by Oxford University Press on behalf of The Royal Astronomical Society.
- id
- 12e152d9-845d-423b-b3ea-614a13fb0fac
- date added to LUP
- 2023-10-04 15:57:13
- date last changed
- 2023-10-09 17:03:27
@article{12e152d9-845d-423b-b3ea-614a13fb0fac,
abstract = {{<p>Catalogue-based studies are of central importance in seismological research, to investigate the temporal, spatial and size distribution of earthquakes in specified study areas. Methods for estimating the fundamental catalogue parameters like the Gutenberg-Richter (G-R) b-value and the completeness magnitude (M<sub>c</sub>) are well established and routinely applied. However, the magnitudes reported in seismicity catalogues contain measurement uncertainties which may significantly distort the estimation of the derived parameters. In this study, we use numerical simulations of synthetic data sets to assess the reliability of different methods for determining b-value and M<sub>c</sub>, assuming the G-R law validity. After contaminating the synthetic catalogues with Gaussian noise (with selected standard deviations), the analysis is performed for numerous data sets of different sample size (N). The noise introduced to the data generally leads to a systematic overestimation of magnitudes close to and above M<sub>c</sub>. This fact causes an increase of the average number of events above M<sub>c</sub>, which in turn leads to an apparent decrease of the b-value. This may result to a significant overestimation of seismicity rate even well above the actual completeness level. The b-value can in general be reliably estimated even for relatively small data sets (N < 1000) when only magnitudes higher than the actual completeness level are used. Nevertheless, a correction of the total number of events belonging in each magnitude class (i.e. 0.1 unit) should be considered, to deal with the magnitude uncertainty effect. Because magnitude uncertainties (here with the form of Gaussian noise) are inevitable in all instrumental catalogues, this finding is fundamental for seismicity rate and seismic hazard assessment analyses. Also important is that for some data analyses significant bias cannot necessarily be avoided by choosing a high M<sub>c</sub> value for analysis. In such cases, there may be a risk of severe miscalculation of seismicity rate regardless the selected magnitude threshold, unless possible bias is properly assessed.</p>}},
author = {{Leptokaropoulos, K. M. and Adamaki, A. K. and Roberts, R. G. and Gkarlaouni, C. G. and Paradisopoulou, P. M.}},
issn = {{0956-540X}},
keywords = {{Numerical approximations and analysis; Statistical methods; Statistical seismology}},
language = {{eng}},
month = {{05}},
number = {{2}},
pages = {{940--951}},
publisher = {{Oxford University Press}},
series = {{Geophysical Journal International}},
title = {{Impact of magnitude uncertainties on seismic catalogue properties}},
url = {{http://dx.doi.org/10.1093/gji/ggy023}},
doi = {{10.1093/gji/ggy023}},
volume = {{213}},
year = {{2018}},
}