Pub Date : 2024-02-04DOI: 10.26443/seismica.v3i1.1099
Peter Makus, Christoph Sens-Schönfelder
We present SeisMIC, a fast, versatile, and adaptable open-source software to estimate seismic velocity changes from ambient seismic noise. SeisMIC includes a broad set of tools and functions to facilitate end-to-end processing of ambient noise data, from data retrieval and raw data analysis via spectrogram computation, over waveform coherence analysis, to post-processing of the final velocity change estimates. A particular highlight of the software is its ability to invert velocity change time series onto a spatial grid, making it possible to create maps of velocity changes. To tackle the challenge of processing large continuous datasets, SeisMIC can exploit multithreading at high efficiency with an about five-time improvement in compute time compared to MSNoise, probably the most widespread ambient noise software. In this manuscript, we provide a short tutorial and tips for users on how to employ SeisMIC most effectively. Extensive and up-to-date documentation is available online. Its broad functionality combined with easy adaptability and high efficiency make SeisMIC a well-suited tool for studies across all scales.
{"title":"SeisMIC - an Open Source Python Toolset to Compute Velocity Changes from Ambient Seismic Noise","authors":"Peter Makus, Christoph Sens-Schönfelder","doi":"10.26443/seismica.v3i1.1099","DOIUrl":"https://doi.org/10.26443/seismica.v3i1.1099","url":null,"abstract":"We present SeisMIC, a fast, versatile, and adaptable open-source software to estimate seismic velocity changes from ambient seismic noise. SeisMIC includes a broad set of tools and functions to facilitate end-to-end processing of ambient noise data, from data retrieval and raw data analysis via spectrogram computation, over waveform coherence analysis, to post-processing of the final velocity change estimates. A particular highlight of the software is its ability to invert velocity change time series onto a spatial grid, making it possible to create maps of velocity changes. To tackle the challenge of processing large continuous datasets, SeisMIC can exploit multithreading at high efficiency with an about five-time improvement in compute time compared to MSNoise, probably the most widespread ambient noise software. In this manuscript, we provide a short tutorial and tips for users on how to employ SeisMIC most effectively. Extensive and up-to-date documentation is available online. Its broad functionality combined with easy adaptability and high efficiency make SeisMIC a well-suited tool for studies across all scales.","PeriodicalId":498743,"journal":{"name":"Seismica","volume":"9 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139867085","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-02-04DOI: 10.26443/seismica.v3i1.1099
Peter Makus, Christoph Sens-Schönfelder
We present SeisMIC, a fast, versatile, and adaptable open-source software to estimate seismic velocity changes from ambient seismic noise. SeisMIC includes a broad set of tools and functions to facilitate end-to-end processing of ambient noise data, from data retrieval and raw data analysis via spectrogram computation, over waveform coherence analysis, to post-processing of the final velocity change estimates. A particular highlight of the software is its ability to invert velocity change time series onto a spatial grid, making it possible to create maps of velocity changes. To tackle the challenge of processing large continuous datasets, SeisMIC can exploit multithreading at high efficiency with an about five-time improvement in compute time compared to MSNoise, probably the most widespread ambient noise software. In this manuscript, we provide a short tutorial and tips for users on how to employ SeisMIC most effectively. Extensive and up-to-date documentation is available online. Its broad functionality combined with easy adaptability and high efficiency make SeisMIC a well-suited tool for studies across all scales.
{"title":"SeisMIC - an Open Source Python Toolset to Compute Velocity Changes from Ambient Seismic Noise","authors":"Peter Makus, Christoph Sens-Schönfelder","doi":"10.26443/seismica.v3i1.1099","DOIUrl":"https://doi.org/10.26443/seismica.v3i1.1099","url":null,"abstract":"We present SeisMIC, a fast, versatile, and adaptable open-source software to estimate seismic velocity changes from ambient seismic noise. SeisMIC includes a broad set of tools and functions to facilitate end-to-end processing of ambient noise data, from data retrieval and raw data analysis via spectrogram computation, over waveform coherence analysis, to post-processing of the final velocity change estimates. A particular highlight of the software is its ability to invert velocity change time series onto a spatial grid, making it possible to create maps of velocity changes. To tackle the challenge of processing large continuous datasets, SeisMIC can exploit multithreading at high efficiency with an about five-time improvement in compute time compared to MSNoise, probably the most widespread ambient noise software. In this manuscript, we provide a short tutorial and tips for users on how to employ SeisMIC most effectively. Extensive and up-to-date documentation is available online. Its broad functionality combined with easy adaptability and high efficiency make SeisMIC a well-suited tool for studies across all scales.","PeriodicalId":498743,"journal":{"name":"Seismica","volume":"1993 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139807433","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-02-01DOI: 10.26443/seismica.v3i1.1084
C. Godano, A. Tramelli, G. Petrillo, Vincenzo Convertito
A very efficient method for estimating the completeness magnitude mc and the scaling parameter b of earthquake magnitude distribution has been thoroughly tested using synthetic seismic catalogues. Subsequently, the method was employed to assess the capability of the b-value in differentiating between foreshocks and aftershocks, confirming previous findings regarding the Amatrice-Norcia earthquake sequence. However, a blind algorithm reveals that the discriminative ability of the b-value necessitates a meticulous selection of the catalogue, thereby reducing the predictability of large events occurring subsequent to a prior major earthquake.
利用合成地震目录对估算地震震级分布的完整性震级 mc 和比例参数 b 的高效方法进行了全面测试。随后，使用该方法评估了 b 值在区分前震和余震方面的能力，证实了之前关于 Amatrice-Norcia 地震序列的研究结果。然而，盲算法显示，b 值的分辨能力要求对地震目录进行细致的选择，从而降低了对之前大地震之后发生的大事件的可预测性。
{"title":"Testing the Predictive Power of b Value for Italian Seismicity","authors":"C. Godano, A. Tramelli, G. Petrillo, Vincenzo Convertito","doi":"10.26443/seismica.v3i1.1084","DOIUrl":"https://doi.org/10.26443/seismica.v3i1.1084","url":null,"abstract":"A very efficient method for estimating the completeness magnitude mc and the scaling parameter b of earthquake magnitude distribution has been thoroughly tested using synthetic seismic catalogues. Subsequently, the method was employed to assess the capability of the b-value in differentiating between foreshocks and aftershocks, confirming previous findings regarding the Amatrice-Norcia earthquake sequence. However, a blind algorithm reveals that the discriminative ability of the b-value necessitates a meticulous selection of the catalogue, thereby reducing the predictability of large events occurring subsequent to a prior major earthquake.","PeriodicalId":498743,"journal":{"name":"Seismica","volume":"75 14","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139873808","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-02-01DOI: 10.26443/seismica.v3i1.1084
C. Godano, A. Tramelli, G. Petrillo, Vincenzo Convertito
A very efficient method for estimating the completeness magnitude mc and the scaling parameter b of earthquake magnitude distribution has been thoroughly tested using synthetic seismic catalogues. Subsequently, the method was employed to assess the capability of the b-value in differentiating between foreshocks and aftershocks, confirming previous findings regarding the Amatrice-Norcia earthquake sequence. However, a blind algorithm reveals that the discriminative ability of the b-value necessitates a meticulous selection of the catalogue, thereby reducing the predictability of large events occurring subsequent to a prior major earthquake.
利用合成地震目录对估算地震震级分布的完整性震级 mc 和比例参数 b 的高效方法进行了全面测试。随后，使用该方法评估了 b 值在区分前震和余震方面的能力，证实了之前关于 Amatrice-Norcia 地震序列的研究结果。然而，盲算法显示，b 值的分辨能力要求对地震目录进行细致的选择，从而降低了对之前大地震之后发生的大事件的可预测性。
{"title":"Testing the Predictive Power of b Value for Italian Seismicity","authors":"C. Godano, A. Tramelli, G. Petrillo, Vincenzo Convertito","doi":"10.26443/seismica.v3i1.1084","DOIUrl":"https://doi.org/10.26443/seismica.v3i1.1084","url":null,"abstract":"A very efficient method for estimating the completeness magnitude mc and the scaling parameter b of earthquake magnitude distribution has been thoroughly tested using synthetic seismic catalogues. Subsequently, the method was employed to assess the capability of the b-value in differentiating between foreshocks and aftershocks, confirming previous findings regarding the Amatrice-Norcia earthquake sequence. However, a blind algorithm reveals that the discriminative ability of the b-value necessitates a meticulous selection of the catalogue, thereby reducing the predictability of large events occurring subsequent to a prior major earthquake.","PeriodicalId":498743,"journal":{"name":"Seismica","volume":"54 16","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139813941","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-01-29DOI: 10.26443/seismica.v3i1.624
C. Fliedner, Melodie French
Seismic waves are used to interpret geologic structure, composition, and environmental conditions in the Earth. However, rocks are not perfectly elastic and their viscoelasticity can dissipate energy during wave propagation. Wave-induced fluid flow mechanisms can cause viscoelasticity resulting in frequency-dependent attenuation, velocities, and elastic moduli (dispersion) in saturated rocks. Dispersion and attenuation are hypothesized to be important in subduction zones, where regions of high fluid content are interpreted below the seismogenic zone. However, this has not been well-tested because of a lack of measurements on relevant lithologies and under saturated conditions. We measured the Young's and shear moduli and the attenuation of a greenschist facies metapelite with the forced oscillation technique at frequencies between 2 x 10-5 and 30 Hz. The moduli and attenuation are frequency-dependent under saturated conditions and depend on the effective pressure. At relatively low effective pressure, the Young's and shear moduli increase by over 50 % between 2 x 10-5 and 30 Hz. We use Standard Linear Solid viscoelastic models to investigate the relationship between the attenuation and dispersion in the Orocopia schist. The models are consistent with the experimental data and demonstrate that viscoelasticity can cause significant dispersion and attenuation in subduction zones.
地震波用于解释地球的地质结构、组成和环境条件。然而，岩石并不是完全弹性的，其粘弹性会在波的传播过程中耗散能量。波浪诱导的流体流动机制可导致粘弹性，从而在饱和岩石中产生与频率相关的衰减、速度和弹性模量（色散）。据推测，频散和衰减在俯冲带中非常重要，因为在俯冲带中，高流体含量区域被解释为发生地震的区域之下。然而，由于缺乏对相关岩性和饱和条件下的测量，这一假设尚未得到很好的验证。我们采用强迫振荡技术，以 2 x 10-5 到 30 Hz 的频率，测量了绿泥石岩相玄武岩的杨氏模量、剪切模量和衰减。在饱和条件下，模量和衰减与频率有关，并取决于有效压力。在相对较低的有效压力下，杨氏模量和剪切模量在 2 x 10-5 和 30 Hz 之间增加了 50%以上。我们使用标准线性固体粘弹性模型来研究奥罗科比亚片岩中衰减和分散之间的关系。这些模型与实验数据一致，并证明粘弹性可在俯冲带造成显著的弥散和衰减。
{"title":"Dispersive Elastic Moduli and Frequency-Dependent Attenuation due to Wave-Induced Fluid Flow in Metapelite","authors":"C. Fliedner, Melodie French","doi":"10.26443/seismica.v3i1.624","DOIUrl":"https://doi.org/10.26443/seismica.v3i1.624","url":null,"abstract":"Seismic waves are used to interpret geologic structure, composition, and environmental conditions in the Earth. However, rocks are not perfectly elastic and their viscoelasticity can dissipate energy during wave propagation. Wave-induced fluid flow mechanisms can cause viscoelasticity resulting in frequency-dependent attenuation, velocities, and elastic moduli (dispersion) in saturated rocks. Dispersion and attenuation are hypothesized to be important in subduction zones, where regions of high fluid content are interpreted below the seismogenic zone. However, this has not been well-tested because of a lack of measurements on relevant lithologies and under saturated conditions. We measured the Young's and shear moduli and the attenuation of a greenschist facies metapelite with the forced oscillation technique at frequencies between 2 x 10-5 and 30 Hz. The moduli and attenuation are frequency-dependent under saturated conditions and depend on the effective pressure. At relatively low effective pressure, the Young's and shear moduli increase by over 50 % between 2 x 10-5 and 30 Hz. We use Standard Linear Solid viscoelastic models to investigate the relationship between the attenuation and dispersion in the Orocopia schist. The models are consistent with the experimental data and demonstrate that viscoelasticity can cause significant dispersion and attenuation in subduction zones.","PeriodicalId":498743,"journal":{"name":"Seismica","volume":"4 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140488653","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-12DOI: 10.26443/seismica.v2i2.1082
Mathijs Koymans, J. Assink, Elske De Zeeuq-van Dalfsen, L. Evers
The electrical network frequency (ENF) of the alternating current operated on the power grid is a well-known source of noise in digital recordings. The noise is widespread and appears not just in close proximity to high-voltage power lines, but also in instruments simply connected to the mains powers grid. This omnipresent, anthropogenic signal is generally perceived as a nuisance in the processing of geophysical data. Research has therefore been mainly focused on its elimination from data, while its benefits have gone largely unexplored. It is shown that mHz fluctuations in the nominal ENF (50-60 Hz) induced by variations in power usage can be accurately extracted from geophysical data. This information represents a persistent time-calibration signal that is coherent between instruments over national scales. Cross-correlation of reliable reference ENF data published by electrical grid operators with estimated ENF data from geophysical recordings allows timing errors to be resolved at the 1 s level. Furthermore, it is shown that a polarization analysis of particle motion at the ENF can detect instrument orientation anomalies. While the source of the ENF signal in geophysical data appears instrument and site specific, its general utility in the detection of timing and orientation anomalies is presented.
{"title":"Passive Assessment of Geophysical Instruments Performance using Electrical Network Frequency Analysis","authors":"Mathijs Koymans, J. Assink, Elske De Zeeuq-van Dalfsen, L. Evers","doi":"10.26443/seismica.v2i2.1082","DOIUrl":"https://doi.org/10.26443/seismica.v2i2.1082","url":null,"abstract":"The electrical network frequency (ENF) of the alternating current operated on the power grid is a well-known source of noise in digital recordings. The noise is widespread and appears not just in close proximity to high-voltage power lines, but also in instruments simply connected to the mains powers grid. This omnipresent, anthropogenic signal is generally perceived as a nuisance in the processing of geophysical data. Research has therefore been mainly focused on its elimination from data, while its benefits have gone largely unexplored. It is shown that mHz fluctuations in the nominal ENF (50-60 Hz) induced by variations in power usage can be accurately extracted from geophysical data. This information represents a persistent time-calibration signal that is coherent between instruments over national scales. Cross-correlation of reliable reference ENF data published by electrical grid operators with estimated ENF data from geophysical recordings allows timing errors to be resolved at the 1 s level. Furthermore, it is shown that a polarization analysis of particle motion at the ENF can detect instrument orientation anomalies. While the source of the ENF signal in geophysical data appears instrument and site specific, its general utility in the detection of timing and orientation anomalies is presented.","PeriodicalId":498743,"journal":{"name":"Seismica","volume":"91 6","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139008314","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-05DOI: 10.26443/seismica.v2i2.1011
Saman Amiri, Alessia Maggi, Mohammad Tatar, D. Zigone, C. Zaroli
In this study, we focus on Northwest Iran and exploit a dataset of Rayleigh-wave group-velocity measurements obtained from ambient noise cross-correlations and earthquakes.We build group-velocity maps using the recently developed SOLA Backus-Gilbert linear tomographic scheme as well as the more traditional Fast-marching Surface-wave Tomography method.The SOLA approach produces robust, unbiased local averages of group velocities with detailed information on their local resolution and uncertainty; however, it does not as yet allow ray-path updates in the inversion process. The Fast-marching method, on the other hand, does allow ray-path updates, although it does not provide information on the resolution and uncertainties of the resulting models (at least not without great computational cost) and may suffer from bias due to model regularisation.The core of this work consists in comparing these two tomographic methods, in particular how they perform in the case of strong vs. weak seismic-velocity contrasts and good vs. poor data coverage. We demonstrate that the only case in which the Fast-marching inversion outperforms the SOLA inversion is for strong anomaly contrasts in regions with good path coverage; in all other configurations, the SOLA inversion produces more coherent anomalies with fewer artefacts.
{"title":"Rayleigh wave group velocities in North-West Iran: SOLA Backus-Gilbert vs. Fast Marching tomographic methods","authors":"Saman Amiri, Alessia Maggi, Mohammad Tatar, D. Zigone, C. Zaroli","doi":"10.26443/seismica.v2i2.1011","DOIUrl":"https://doi.org/10.26443/seismica.v2i2.1011","url":null,"abstract":"In this study, we focus on Northwest Iran and exploit a dataset of Rayleigh-wave group-velocity measurements obtained from ambient noise cross-correlations and earthquakes.We build group-velocity maps using the recently developed SOLA Backus-Gilbert linear tomographic scheme as well as the more traditional Fast-marching Surface-wave Tomography method.The SOLA approach produces robust, unbiased local averages of group velocities with detailed information on their local resolution and uncertainty; however, it does not as yet allow ray-path updates in the inversion process. The Fast-marching method, on the other hand, does allow ray-path updates, although it does not provide information on the resolution and uncertainties of the resulting models (at least not without great computational cost) and may suffer from bias due to model regularisation.The core of this work consists in comparing these two tomographic methods, in particular how they perform in the case of strong vs. weak seismic-velocity contrasts and good vs. poor data coverage. We demonstrate that the only case in which the Fast-marching inversion outperforms the SOLA inversion is for strong anomaly contrasts in regions with good path coverage; in all other configurations, the SOLA inversion produces more coherent anomalies with fewer artefacts.","PeriodicalId":498743,"journal":{"name":"Seismica","volume":"3 6","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138601175","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-14DOI: 10.26443/seismica.v2i3.1083
Xiaotian Ding, Shiqing Xu, Yuqing Xie, Martijn Van den Ende, Jan Premus, Jean-Paul Ampuero
Multiple lines of evidence indicate that the 2023 Mw 7.8 Kahramanmaraş (Türkiye) earthquake started on a splay fault, then branched bilaterally onto the nearby East Anatolian Fault (EAF). This rupture pattern includes one feature previously deemed implausible, called backward rupture branching: rupture propagating from the splay fault onto the SW EAF segment through a sharp corner (with an acute angle between the two faults). To understand this feature, we perform 2.5-D dynamic rupture simulations considering a large set of possible scenarios. We find that both subshear and supershear ruptures on the splay fault can trigger bilateral ruptures on the EAF, which themselves can be either subshear, supershear, or a mixture of the two. In most cases, rupture on the SW segment of the EAF starts after rupture onset on its NE segment: the SW rupture is triggered by the NE rupture. Only when the EAF has initial stresses very close to failure can its SW segment be directly triggered by the initial splay-fault rupture, earlier than the activation of the NE segment. These results advance our understanding of the mechanisms of multi-segment rupture and the complexity of rupture processes, paving the way for a more accurate assessment of earthquake hazards.
{"title":"The sharp turn: Backward rupture branching during the 2023 Mw 7.8 Kahramanmaraş (Türkiye) earthquake","authors":"Xiaotian Ding, Shiqing Xu, Yuqing Xie, Martijn Van den Ende, Jan Premus, Jean-Paul Ampuero","doi":"10.26443/seismica.v2i3.1083","DOIUrl":"https://doi.org/10.26443/seismica.v2i3.1083","url":null,"abstract":"Multiple lines of evidence indicate that the 2023 Mw 7.8 Kahramanmaraş (Türkiye) earthquake started on a splay fault, then branched bilaterally onto the nearby East Anatolian Fault (EAF). This rupture pattern includes one feature previously deemed implausible, called backward rupture branching: rupture propagating from the splay fault onto the SW EAF segment through a sharp corner (with an acute angle between the two faults). To understand this feature, we perform 2.5-D dynamic rupture simulations considering a large set of possible scenarios. We find that both subshear and supershear ruptures on the splay fault can trigger bilateral ruptures on the EAF, which themselves can be either subshear, supershear, or a mixture of the two. In most cases, rupture on the SW segment of the EAF starts after rupture onset on its NE segment: the SW rupture is triggered by the NE rupture. Only when the EAF has initial stresses very close to failure can its SW segment be directly triggered by the initial splay-fault rupture, earlier than the activation of the NE segment. These results advance our understanding of the mechanisms of multi-segment rupture and the complexity of rupture processes, paving the way for a more accurate assessment of earthquake hazards.","PeriodicalId":498743,"journal":{"name":"Seismica","volume":"12 9","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134991265","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The creation of a homogenized earthquake catalog is a fundamental step in seismic hazard analysis. The homogenization procedure, however, is complex and requires a good understanding of the heterogeneities among the available bulletins. Common events within the bulletins have to be identified and assigned with the most suitable origin time and location solution, while all the events have to be harmonized into a single magnitude scale. This process entails several decision variables that are usually defined using qualitative measures or expert opinion, without a clear exploration of the associated uncertainties. To address this issue, we present an automated and data-driven workflow that defines spatio-temporal margins within which duplicate events fall and converts the various reported magnitudes into a common scale. Special attention has been paid to the fitted functional form and the validity range of the derived magnitude conversion relations. The proposed methodology has been successfully applied to a wide region around the Dead Sea Transform Fault Zone (27N-36N, 31E-39E), with input data from various sources such as the International Seismological Centre and the Geophysical Institute of Israel. The produced public catalog contains more than 5500 events, between 1900 and 2017, with moment magnitude Mw above 3. The MATLAB/Python scripts used in this study are also available.
{"title":"Homogenizing instrumental earthquake catalogs – a case study around the Dead Sea Transform Fault Zone","authors":"Iason Grigoratos, Valerio Poggi, Laurentiu Danciu, Ricardo Monteiro","doi":"10.26443/seismica.v2i2.402","DOIUrl":"https://doi.org/10.26443/seismica.v2i2.402","url":null,"abstract":"The creation of a homogenized earthquake catalog is a fundamental step in seismic hazard analysis. The homogenization procedure, however, is complex and requires a good understanding of the heterogeneities among the available bulletins. Common events within the bulletins have to be identified and assigned with the most suitable origin time and location solution, while all the events have to be harmonized into a single magnitude scale. This process entails several decision variables that are usually defined using qualitative measures or expert opinion, without a clear exploration of the associated uncertainties. To address this issue, we present an automated and data-driven workflow that defines spatio-temporal margins within which duplicate events fall and converts the various reported magnitudes into a common scale. Special attention has been paid to the fitted functional form and the validity range of the derived magnitude conversion relations. The proposed methodology has been successfully applied to a wide region around the Dead Sea Transform Fault Zone (27N-36N, 31E-39E), with input data from various sources such as the International Seismological Centre and the Geophysical Institute of Israel. The produced public catalog contains more than 5500 events, between 1900 and 2017, with moment magnitude Mw above 3. The MATLAB/Python scripts used in this study are also available.","PeriodicalId":498743,"journal":{"name":"Seismica","volume":"3 9‐10","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135480052","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-27DOI: 10.26443/seismica.v2i2.285
Olivier Lengliné, Joachim Rimpôt, Alessia Maggi, Dimitri Zigone
The Kerguelen archipelago, one of the largest oceanic archipelagos in the world, was built by an active hotspot interacting with a ridge between 110 and 40 million years ago; since then, the ridge has migrated over 1000~km away and the archipelago's volcanic activity has been steadily decreasing. Despite the lack of recent active tectonics and the quiescent volcanism of the Kerguelen archipelago, there have been several observations of seismic events of unknown origin in its vicinity. The only seismic instrument within 1000~km of the archipelago was installed on Kerguelen's main island in the 1980's. In this study we apply modern earthquake detection techniques to the continuous waveforms recorded by this seismometer over the past 20 years. We reveal that the Kerguelen archipelago islands hosts an abundant seismicity. This seismicity exhibits swarm-like characteristics in several clusters while at other locations the earthquakes appear more steady over time. We locate most events near the largest icecap of the main island. We speculate that the origin of the earthquakes can be linked to residual volcanic, magmatic, or hydrothermal activity at depth, all of which can be favored by flexural stress caused by the documented fast retreat of icecap. This seismicity may also indicate that the Kerguelen hotspot shows signs of unrest.
{"title":"Recent seismicity on the Kerguelen islands","authors":"Olivier Lengliné, Joachim Rimpôt, Alessia Maggi, Dimitri Zigone","doi":"10.26443/seismica.v2i2.285","DOIUrl":"https://doi.org/10.26443/seismica.v2i2.285","url":null,"abstract":"The Kerguelen archipelago, one of the largest oceanic archipelagos in the world, was built by an active hotspot interacting with a ridge between 110 and 40 million years ago; since then, the ridge has migrated over 1000~km away and the archipelago's volcanic activity has been steadily decreasing. Despite the lack of recent active tectonics and the quiescent volcanism of the Kerguelen archipelago, there have been several observations of seismic events of unknown origin in its vicinity. The only seismic instrument within 1000~km of the archipelago was installed on Kerguelen's main island in the 1980's. In this study we apply modern earthquake detection techniques to the continuous waveforms recorded by this seismometer over the past 20 years. We reveal that the Kerguelen archipelago islands hosts an abundant seismicity. This seismicity exhibits swarm-like characteristics in several clusters while at other locations the earthquakes appear more steady over time. We locate most events near the largest icecap of the main island. We speculate that the origin of the earthquakes can be linked to residual volcanic, magmatic, or hydrothermal activity at depth, all of which can be favored by flexural stress caused by the documented fast retreat of icecap. This seismicity may also indicate that the Kerguelen hotspot shows signs of unrest.","PeriodicalId":498743,"journal":{"name":"Seismica","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136262180","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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