L. Nannipieri, Andrea Bevilacqua, F. Di Traglia, M. Favalli, A. Fornaciai
Stromboli is a volcanic island in a persistent state of activity, located in the Tyrrhenian Sea off the northern coast of Sicily. During the night of 25 and 26 May 2022, a massive human-caused wildfire destroyed most of the vegetation cover on the NE flank of the island, just above the main village. On 12 August 2022, a particularly heavy rainfall event remobilized the loose volcaniclastic deposits that covered the burned volcanic flank, no longer protected by the vegetation. This event triggered several debris flows that were channeled by the roads and flooded several streets and buildings, causing severe damage to the village. In late-March 2023, just before the large spring vegetation growth, we conducted an Unmanned Aerial System (UAS) photogrammetric campaign over a sector of the NE flank of Stromboli Island, to acquire data on an area massively affected by the wildfire first and by the debris flows later. Here we present and share with the scientific community and civil authorities the results of this UAS campaign, which consists of a 1.4 km2 wide 10 cm-resolution Digital Surface Model (DSM) and 1.6 cm-resolution orthomosaic. These data clearly show the dramatic consequences of the 2022 tragic events at Stromboli. We also produced an elevation difference map by comparing the 2023 DSM here generated and the 2012 LiDAR DEM to provide a first overview of the thickness of the deposits that were removed from the Stromboli NE flank.
{"title":"The March 2023 UAS-based high-resolution Digital Surface Model and orthomosaic of the NE flank of Stromboli volcano (Sicily, Italy)","authors":"L. Nannipieri, Andrea Bevilacqua, F. Di Traglia, M. Favalli, A. Fornaciai","doi":"10.4401/ag-8982","DOIUrl":"https://doi.org/10.4401/ag-8982","url":null,"abstract":"Stromboli is a volcanic island in a persistent state of activity, located in the Tyrrhenian Sea off the northern coast of Sicily. During the night of 25 and 26 May 2022, a massive human-caused wildfire destroyed most of the vegetation cover on the NE flank of the island, just above the main village. On 12 August 2022, a particularly heavy rainfall event remobilized the loose volcaniclastic deposits that covered the burned volcanic flank, no longer protected by the vegetation. This event triggered several debris flows that were channeled by the roads and flooded several streets and buildings, causing severe damage to the village. In late-March 2023, just before the large spring vegetation growth, we conducted an Unmanned Aerial System (UAS) photogrammetric campaign over a sector of the NE flank of Stromboli Island, to acquire data on an area massively affected by the wildfire first and by the debris flows later. Here we present and share with the scientific community and civil authorities the results of this UAS campaign, which consists of a 1.4 km2 wide 10 cm-resolution Digital Surface Model (DSM) and 1.6 cm-resolution orthomosaic. These data clearly show the dramatic consequences of the 2022 tragic events at Stromboli. We also produced an elevation difference map by comparing the 2023 DSM here generated and the 2012 LiDAR DEM to provide a first overview of the thickness of the deposits that were removed from the Stromboli NE flank.","PeriodicalId":50766,"journal":{"name":"Annals of Geophysics","volume":"77 13","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138956762","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The main aims of this study were to i) investigate the impact of erosion factors including land use, slope position, and lithology on magnetic susceptibility (MS) of soil, and ii) detecting the pedogenic effect on MS enhancement using simple methods, including median absolute deviation (MAD), topsoil-subsoil difference methods, MS magnitude and Dearing’s model. Soil cores were sampled along five slope positions in two transects selected in forested and cultivated lands in a watershed located in north of Morocco. The results showed higher values of MS in the upperslopes in forested land due to soil stability, and lower ones in middleslopes and lowerslopes due to soil erosion. However, MS is higher in cultivated land in middleslopes due to soil deposition and it is lower in the upperslopes due to erosion. The results confirmed the pedogenic effect on MS. This is confirmed by i) enhanced Forster factor and low values of magnetic susceptibility background, ii) dominance of ultrafine super-paramagnetic/stable single-domain ferrimagnetic grains in almost all studied soils, and iii) absence of anomaly in MAD data set and pertinence of the results of MAD and topsoil-subsoil difference methods.
本研究的主要目的是：i) 研究侵蚀因素（包括土地利用、斜坡位置和岩性）对土壤磁感应强度（MS）的影响；ii) 使用简单的方法（包括绝对偏差中值法、表土-底土差异法、MS 幅值和 Dearing 模型）检测土壤磁感应强度的成土效应。在摩洛哥北部一个流域的林地和耕地中选取了两个横断面的五个斜坡位置进行土壤取样。结果表明，由于土壤稳定性，林地上坡的 MS 值较高，而由于土壤侵蚀，中坡和低坡的 MS 值较低。然而，在耕地中，由于土壤沉积，中坡的 MS 值较高，而由于土壤侵蚀，上坡的 MS 值较低。结果证实了对 MS 的成土效应。具体表现为：i) 福斯特因子增强，磁感应强度背景值低；ii) 几乎所有研究土壤中都以超细超顺磁性/稳定单域铁磁性颗粒为主；iii) MAD 数据集没有异常，MAD 和表土-底土差分法的结果具有相关性。
{"title":"Pedogenic effect and the impact of erosion factors on topsoil magnetic susceptibility enhancement","authors":"N. Bouhsane, S. Bouhlassa","doi":"10.4401/ag-8896","DOIUrl":"https://doi.org/10.4401/ag-8896","url":null,"abstract":"The main aims of this study were to i) investigate the impact of erosion factors including land use, slope position, and lithology on magnetic susceptibility (MS) of soil, and ii) detecting the pedogenic effect on MS enhancement using simple methods, including median absolute deviation (MAD), topsoil-subsoil difference methods, MS magnitude and Dearing’s model. Soil cores were sampled along five slope positions in two transects selected in forested and cultivated lands in a watershed located in north of Morocco. The results showed higher values of MS in the upperslopes in forested land due to soil stability, and lower ones in middleslopes and lowerslopes due to soil erosion. However, MS is higher in cultivated land in middleslopes due to soil deposition and it is lower in the upperslopes due to erosion. The results confirmed the pedogenic effect on MS. This is confirmed by i) enhanced Forster factor and low values of magnetic susceptibility background, ii) dominance of ultrafine super-paramagnetic/stable single-domain ferrimagnetic grains in almost all studied soils, and iii) absence of anomaly in MAD data set and pertinence of the results of MAD and topsoil-subsoil difference methods.","PeriodicalId":50766,"journal":{"name":"Annals of Geophysics","volume":"11 5","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139169536","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Benella, G. Consolini, M. Stumpo, Tommaso Alberti
The near-Earth electromagnetic environment represents a far-from-equilibrium system characterized by sudden irregular energy relaxation events. For a broad class of complex systems, time series can be interpreted in terms of a superposition of stochastic and deterministic components occurring at different time scales. In this work we use the generalization of the SYM-H index provided by the SuperMAG collaboration (SMR), which is meant for monitoring the global variation of the horizontal component of the Earth’s magnetic field in the near-equatorial regions. The aim of this work is to model the SMR dynamics via stochastic differential equations thus providing a semi-empirical model whose parameters are retained from data. As a first step we test the Markov condition on the SMR data sample, which represents the basic condition for our stochastic modeling, and we show that such a requirement is accurately satisfied by SMR time series. This allows us to infer the model parameters for the SMR index through the Kramers–Moyal analysis. Finally, we give evidence that a purely diffusive process is not representative of the observed dynamics and then a model based on jump-diffusion processes must be considered to correctly reproduce the dynamical features of the SMR index.
{"title":"A semi-empirical model for magnetic storm dynamics","authors":"S. Benella, G. Consolini, M. Stumpo, Tommaso Alberti","doi":"10.4401/ag-9022","DOIUrl":"https://doi.org/10.4401/ag-9022","url":null,"abstract":"The near-Earth electromagnetic environment represents a far-from-equilibrium system characterized by sudden irregular energy relaxation events. For a broad class of complex systems, time series can be interpreted in terms of a superposition of stochastic and deterministic components occurring at different time scales. In this work we use the generalization of the SYM-H index provided by the SuperMAG collaboration (SMR), which is meant for monitoring the global variation of the horizontal component of the Earth’s magnetic field in the near-equatorial regions. The aim of this work is to model the SMR dynamics via stochastic differential equations thus providing a semi-empirical model whose parameters are retained from data. As a first step we test the Markov condition on the SMR data sample, which represents the basic condition for our stochastic modeling, and we show that such a requirement is accurately satisfied by SMR time series. This allows us to infer the model parameters for the SMR index through the Kramers–Moyal analysis. Finally, we give evidence that a purely diffusive process is not representative of the observed dynamics and then a model based on jump-diffusion processes must be considered to correctly reproduce the dynamical features of the SMR index.","PeriodicalId":50766,"journal":{"name":"Annals of Geophysics","volume":"22 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139217343","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Earthquake catalogs include dependent earthquakes, which are spatiotemporally related, and independent or background earthquakes. In order to predict long-term seismicity or conduct a seismic hazard assessment, the dependent earthquakes must be removed to generate a declustered earthquake catalog. Several declustering methods have been proposed to date; however, the result of seismic hazard assessment may vary depending on which declustering methods are selected. In the present study, the catalog of earthquakes that were observed between 2016 and 2021 in and around the Korean Peninsula is declustered using the methods proposed by Gardner and Knopoff [1974], Reasenberg [1985], and Zhuang et al. [2002], and the resultant catalogs are compared. The seismicity parameters (a- and b-values) in the Gutenberg-Richter relationship are found to vary among the three declustered catalogs, thus affecting long-term earthquake predictions and seismic hazard assessment. The raw (original) and three declustered catalogs are also tested to see whether they follow the Poisson process. The minimum magnitude ( ) above which the null hypothesis of the Poisson process cannot be rejected in the earthquake catalogs ranges from 1.6 to 2.2, depending on the declustered catalog. Further, the obtained herein shows a large value compared to the completeness magnitude estimated in the present study. Comparing the curves representing the cumulative number of background earthquakes against the elapsed time for the declustered catalogs shows that the method by Zhuang et al. [2002] produces the result in the closest agreement with the real background seismicity curve.
地震目录包括时空相关的依赖地震和独立地震或背景地震。为了预测长期的地震活动性或进行地震危险性评估，必须去除相关地震以生成分集地震目录。目前已经提出了几种聚类方法;然而，不同的聚类方法可能会导致地震危险性评估的结果不同。在本研究中，采用Gardner and Knopoff[1974]、Reasenberg[1985]和Zhuang等[2002]提出的方法对朝鲜半岛及其周边地区2016年至2021年观测到的地震目录进行了分类，并对所得目录进行了比较。发现古腾堡-里希特关系中的地震活动性参数(a-值和b值)在三个散类目录中有所不同，从而影响长期地震预测和地震危险性评估。原始的(原始的)和三个分离的星表也被测试，看它们是否遵循泊松过程。在地震目录中，泊松过程的零假设不能被拒绝的最小震级()的范围从1.6到2.2，取决于分散的目录。此外，与本研究中估计的完备程度相比，本文获得的结果显示出较大的值。将表示背景地震累积次数的曲线与聚类目录的经过时间进行比较表明，庄等人[2002]的方法产生的结果与实际背景地震活动曲线最接近。
{"title":"Comparison of earthquake catalogs for the Korean Peninsula declustered using three different methods","authors":"Sung Kyun Kim","doi":"10.4401/ag-8965","DOIUrl":"https://doi.org/10.4401/ag-8965","url":null,"abstract":"Earthquake catalogs include dependent earthquakes, which are spatiotemporally related, and independent or background earthquakes. In order to predict long-term seismicity or conduct a seismic hazard assessment, the dependent earthquakes must be removed to generate a declustered earthquake catalog. Several declustering methods have been proposed to date; however, the result of seismic hazard assessment may vary depending on which declustering methods are selected. In the present study, the catalog of earthquakes that were observed between 2016 and 2021 in and around the Korean Peninsula is declustered using the methods proposed by Gardner and Knopoff [1974], Reasenberg [1985], and Zhuang et al. [2002], and the resultant catalogs are compared. The seismicity parameters (a- and b-values) in the Gutenberg-Richter relationship are found to vary among the three declustered catalogs, thus affecting long-term earthquake predictions and seismic hazard assessment. The raw (original) and three declustered catalogs are also tested to see whether they follow the Poisson process. The minimum magnitude ( ) above which the null hypothesis of the Poisson process cannot be rejected in the earthquake catalogs ranges from 1.6 to 2.2, depending on the declustered catalog. Further, the obtained herein shows a large value compared to the completeness magnitude estimated in the present study. Comparing the curves representing the cumulative number of background earthquakes against the elapsed time for the declustered catalogs shows that the method by Zhuang et al. [2002] produces the result in the closest agreement with the real background seismicity curve.","PeriodicalId":50766,"journal":{"name":"Annals of Geophysics","volume":" 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135242868","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
E. M. Takla, Sukir Maryanto, Akimasa Yoshikawa, Teiji Uozumi
Studying Pc3-4 geomagnetic pulsations at equatorial and very low latitude regions is an important issue to understand their generation and propagation mechanisms. Pc3-4 amplitudes and their latitudinal dependency across the dip equator up to low latitudes (± 25°) are investigated using geomagnetic data simultaneously obtained by the MAGDAS/CPMN stations along the 210° Magnetic Meridian (MM) chain. Forty-five Pc3 events and thirty-two Pc4 events were selected for this study. Our results show a clear dependence of Pc3-4 amplitudes on geomagnetic latitudes. At the dip equator, most of the selected Pc3 events (~75%) showed an enhancement in amplitudes, while the rest (~25%) showed an attenuation. After that, the amplitudes decreased gradually by increasing latitudes. These results suggest mixed generation and propagation mechanisms for the equatorial and very low latitudes Pc3s. For better understanding, the Interplanetary Magnetic Field (IMF) and solar conditions are examined during the selected events. Results indicate that Pc3 events with enhanced amplitudes at dip equator are mainly occurred in daytime with no preference to IMF (magnitude and direction) and solar parameters, which suggests the ionospheric currents model as a generation and propagation mechanism for these events. While the attenuation observed in the other Pc3 events was associated with intense and abrupt fluctuations in the IMF and solar parameters, which in turn suggests the compressional wave model for generating these Pc3 events. On the other hand, these two models can explain the observed enhancement in the Pc4 amplitudes at the dip equator. Therefore, our obtained results clarified the origin of equatorial Pc3-4 pulsations.
{"title":"Latitudinal dependence of Pc3-4 amplitudes across the dip equator along the 210º Magnetic Meridian","authors":"E. M. Takla, Sukir Maryanto, Akimasa Yoshikawa, Teiji Uozumi","doi":"10.4401/ag-8979","DOIUrl":"https://doi.org/10.4401/ag-8979","url":null,"abstract":"Studying Pc3-4 geomagnetic pulsations at equatorial and very low latitude regions is an important issue to understand their generation and propagation mechanisms. Pc3-4 amplitudes and their latitudinal dependency across the dip equator up to low latitudes (± 25°) are investigated using geomagnetic data simultaneously obtained by the MAGDAS/CPMN stations along the 210° Magnetic Meridian (MM) chain. Forty-five Pc3 events and thirty-two Pc4 events were selected for this study. Our results show a clear dependence of Pc3-4 amplitudes on geomagnetic latitudes. At the dip equator, most of the selected Pc3 events (~75%) showed an enhancement in amplitudes, while the rest (~25%) showed an attenuation. After that, the amplitudes decreased gradually by increasing latitudes. These results suggest mixed generation and propagation mechanisms for the equatorial and very low latitudes Pc3s. For better understanding, the Interplanetary Magnetic Field (IMF) and solar conditions are examined during the selected events. Results indicate that Pc3 events with enhanced amplitudes at dip equator are mainly occurred in daytime with no preference to IMF (magnitude and direction) and solar parameters, which suggests the ionospheric currents model as a generation and propagation mechanism for these events. While the attenuation observed in the other Pc3 events was associated with intense and abrupt fluctuations in the IMF and solar parameters, which in turn suggests the compressional wave model for generating these Pc3 events. On the other hand, these two models can explain the observed enhancement in the Pc4 amplitudes at the dip equator. Therefore, our obtained results clarified the origin of equatorial Pc3-4 pulsations.","PeriodicalId":50766,"journal":{"name":"Annals of Geophysics","volume":"17 5","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135680061","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
P-wave reflection and transmission coefficients for non-welded interface play crucial roles in broad practical engineering productions, involving fracture properties prediction and seismic inversion. However, the existing reflection coefficient equations for non-welded interface in elasto-plastic media are seldom studied, although the elasto-plastic deformation is frequently encountered in the Earth’s subsurface due to artificial and tectonic activities. In this study, we proposed the accurate reflection and transmission coefficients equation for a non-welded interface embedded in an elasto-plastic deformed medium based on the elasto-plastic acoustoelastic and linear-slip theory. In detail, this paper uses elasto-plastic acoustoelastic theory to derive the reflection and transmission coefficients equation. The reflection and transmission coefficients matrix are solved using the linear-slip theory as the boundary condition. Moreover, we use the hardening parameter and plastic deformation to represent the plastic properties of the rock, which is a function of stress and plastic deformation. Through Numerical analysis, the deformation caused by static stress has significantly changed the amplitude and the slope of the reflection and transmission coefficients amplitude. As the stress increases, the rock’s velocity becomes higher, and all reflection and transmission coefficients (i.e., RPP, RPS, TPP, TPS) abruptly change at the critical angle. Furthermore, with the increase in plastic deformation, the critical angle of the incident P-wave and the hardening parameter becomes larger than the unstressed state. The non-welded interface exhibits a low-pass frequency filter for reflected SV-waves and a high-pass frequency filter for reflected P-waves and transmitted P and SV waves. In addition, we can observe that static vertical stress can weaken the anomalous reflections caused by non-welded formations, but the effect is insignificant. On the other hand, the effect of fracture normal compliance to reflection and transmission is detailly investigated. When N<2.5*10-10(MPa-1), The non-welded interface is close to the welded interface, while N>2.5*10-5(MPa-1), the non-welded interface is close to the solid-air interface.
{"title":"Accurate P-wave reflection and transmission coefficients for non-welded interface incorporating elasto-plastic deformation","authors":"Zihang Fan, Zhaoyun Zong, Fubin Chen","doi":"10.4401/ag-8909","DOIUrl":"https://doi.org/10.4401/ag-8909","url":null,"abstract":"P-wave reflection and transmission coefficients for non-welded interface play crucial roles in broad practical engineering productions, involving fracture properties prediction and seismic inversion. However, the existing reflection coefficient equations for non-welded interface in elasto-plastic media are seldom studied, although the elasto-plastic deformation is frequently encountered in the Earth’s subsurface due to artificial and tectonic activities. In this study, we proposed the accurate reflection and transmission coefficients equation for a non-welded interface embedded in an elasto-plastic deformed medium based on the elasto-plastic acoustoelastic and linear-slip theory. In detail, this paper uses elasto-plastic acoustoelastic theory to derive the reflection and transmission coefficients equation. The reflection and transmission coefficients matrix are solved using the linear-slip theory as the boundary condition. Moreover, we use the hardening parameter and plastic deformation to represent the plastic properties of the rock, which is a function of stress and plastic deformation. Through Numerical analysis, the deformation caused by static stress has significantly changed the amplitude and the slope of the reflection and transmission coefficients amplitude. As the stress increases, the rock’s velocity becomes higher, and all reflection and transmission coefficients (i.e., RPP, RPS, TPP, TPS) abruptly change at the critical angle. Furthermore, with the increase in plastic deformation, the critical angle of the incident P-wave and the hardening parameter becomes larger than the unstressed state. The non-welded interface exhibits a low-pass frequency filter for reflected SV-waves and a high-pass frequency filter for reflected P-waves and transmitted P and SV waves. In addition, we can observe that static vertical stress can weaken the anomalous reflections caused by non-welded formations, but the effect is insignificant. On the other hand, the effect of fracture normal compliance to reflection and transmission is detailly investigated. When N<2.5*10-10(MPa-1), The non-welded interface is close to the welded interface, while N>2.5*10-5(MPa-1), the non-welded interface is close to the solid-air interface.","PeriodicalId":50766,"journal":{"name":"Annals of Geophysics","volume":"58 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135684212","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Large earthquakes mean recurrence time (Tr) on specific fault segments is one of the primary input parameters for developing long-term Earthquake Rupture Forecast (ERF) models in a specific time span considering either a time-independent or an elastic rebound motivated renewal assumption. An attempt is made to define Tr on the major fault segments comprised in Kefalonia Transform Fault Zone (KTFZ), which is an active boundary demarcating from the west the area of central Ionian Islands, namely Lefkada and Kefalonia, and is associated with remarkably high seismic activity. Frequent large (Mw ≥ 6.0) earthquakes are reported to have caused severe damage during the last six centuries. Although the number of large earthquakes (including both historical and instrumental) is satisfactory enough for regional hazard studies, their number become very limited when they are subdivided into subsets assigned to specific fault segments. Physics-based earthquake simulators are approaches to overcome recurrence intervals shortage, due to their ability to generate long lasting earthquake catalogs. The application of a physics-based simulatorn the KTFZ, is attemped upon a detailed fault network model and implemented multiple times and with a wide range of input parameters, aiming at the definition of the most representative simulated catalog in respect to the observed regional seismicity. The most representative simulated catalog is finally used for investigating the recurrence behavior of large (Mw ≥ 6.0) earthquakes and assessing whether the renewal model performs better that the Poisson model, after considering both individual and multiple ruptured segments scenarios.
{"title":"Large Earthquakes Recurrence Time in the Kefalonia Transform Fault Zone (KTFZ), Greece: Results from a physics-based simulator approach","authors":"Christos Kourouklas, Rodolfo Console, Eleftheria Papadimitriou, Vassilios Karakostas, Maura Murru","doi":"10.4401/ag-8936","DOIUrl":"https://doi.org/10.4401/ag-8936","url":null,"abstract":"Large earthquakes mean recurrence time (Tr) on specific fault segments is one of the primary input parameters for developing long-term Earthquake Rupture Forecast (ERF) models in a specific time span considering either a time-independent or an elastic rebound motivated renewal assumption. An attempt is made to define Tr on the major fault segments comprised in Kefalonia Transform Fault Zone (KTFZ), which is an active boundary demarcating from the west the area of central Ionian Islands, namely Lefkada and Kefalonia, and is associated with remarkably high seismic activity. Frequent large (Mw ≥ 6.0) earthquakes are reported to have caused severe damage during the last six centuries. Although the number of large earthquakes (including both historical and instrumental) is satisfactory enough for regional hazard studies, their number become very limited when they are subdivided into subsets assigned to specific fault segments. Physics-based earthquake simulators are approaches to overcome recurrence intervals shortage, due to their ability to generate long lasting earthquake catalogs. The application of a physics-based simulatorn the KTFZ, is attemped upon a detailed fault network model and implemented multiple times and with a wide range of input parameters, aiming at the definition of the most representative simulated catalog in respect to the observed regional seismicity. The most representative simulated catalog is finally used for investigating the recurrence behavior of large (Mw ≥ 6.0) earthquakes and assessing whether the renewal model performs better that the Poisson model, after considering both individual and multiple ruptured segments scenarios.","PeriodicalId":50766,"journal":{"name":"Annals of Geophysics","volume":"24 5","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135873372","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ground Motion Prediction Equation (GMPE) is one of the significantly important tools to perform the seismic hazards analysis of any region. Therefore, the development of GMPEs at the bedrock level is utmost important especially when the region does not have any earthquake recording stations. The present study discussed the development of a GMPE at bedrock level for the Bihar region based on the stochastic model. The different seismic parameters such as magnitudes (Mw) 4.0‐8.5, spectral periods of 0‐10 s and distances up to 300 km have been considered for the stochastic model. Based on the results, it was found that the stochastic model is capable to predict the ground motion synthetically and the proposed GMPE, for Bihar region, predicts the spectral acceleration in most precise way. Further, the ground motion amplification analysis was carried out using synthetically generated bedrock motion to analyze the effect of soil deposits on the amplification or de‐amplification of the bedrock peak ground acceleration. It was found that that the seismic wave gets amplified at ground level by 10% to 70% from the input motion PGA ranging from 0.175g‐0.435g, indicating amplification and de‐amplification of seismic wave. The maximum spectral acceleration at surface level was also found to be increased by approximately 60%, 56% and 27%, when bedrock input motion of PGA = 0.175g, 0.256g and 0.435g, respectively. Thus, based on the results, it can be stated that the developed GMPE can be used to assess the seismic hazards analysis in Bihar region. Further, it can be suggested that there is a need of the development of a predictive attenuation relationship at the surface level PGA, for Bihar region or any earthquake prone area, incorporating different site classes and regional seismicity since, the seismic wave amplified due to the presence of soil deposits.
{"title":"Development of Synthetic Ground Motion-based Attenuation Relationship for Bihar Region for Seismic Ground Response Analysis Considering Central Seismic Gap","authors":"Prabhakar Kumar, Shiv Shankar Kumar, Harinarayan Nelliparanbill Hareeshkumar","doi":"10.4401/ag-8889","DOIUrl":"https://doi.org/10.4401/ag-8889","url":null,"abstract":"Ground Motion Prediction Equation (GMPE) is one of the significantly important tools to perform the seismic hazards analysis of any region. Therefore, the development of GMPEs at the bedrock level is utmost important especially when the region does not have any earthquake recording stations. The present study discussed the development of a GMPE at bedrock level for the Bihar region based on the stochastic model. The different seismic parameters such as magnitudes (Mw) 4.0‐8.5, spectral periods of 0‐10 s and distances up to 300 km have been considered for the stochastic model. Based on the results, it was found that the stochastic model is capable to predict the ground motion synthetically and the proposed GMPE, for Bihar region, predicts the spectral acceleration in most precise way. Further, the ground motion amplification analysis was carried out using synthetically generated bedrock motion to analyze the effect of soil deposits on the amplification or de‐amplification of the bedrock peak ground acceleration. It was found that that the seismic wave gets amplified at ground level by 10% to 70% from the input motion PGA ranging from 0.175g‐0.435g, indicating amplification and de‐amplification of seismic wave. The maximum spectral acceleration at surface level was also found to be increased by approximately 60%, 56% and 27%, when bedrock input motion of PGA = 0.175g, 0.256g and 0.435g, respectively. Thus, based on the results, it can be stated that the developed GMPE can be used to assess the seismic hazards analysis in Bihar region. Further, it can be suggested that there is a need of the development of a predictive attenuation relationship at the surface level PGA, for Bihar region or any earthquake prone area, incorporating different site classes and regional seismicity since, the seismic wave amplified due to the presence of soil deposits.","PeriodicalId":50766,"journal":{"name":"Annals of Geophysics","volume":"19 2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136233549","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Numerical Weather Prediction (NWP) models exhibit systematic errors in the forecast of near surface atmospheric parameters due to various factors like grid resolution, parameterization schemes, treatment of sub-grid scale phenomena, data for initial and boundary conditions and interpolation techniques. One of the methods for reduction in model errors is the use of Kalman filter algorithm which recursively combines model output and observations such that the systematic errors are minimized. In the present study, the Kalman filter algorithm is utilized for correction of model output from The Air Pollution Model (TAPM) for the year 2013. The variables corrected are 2-m air temperature, 2-m relative humidity and zonal and meridional wind components at 10-m. Hourly observations of the same variables available at Trombay site are used in the study. In the present study, it is seen that, both wind speed and wind direction are better reproduced after Kalman filtering, in addition to near surface air temperature and relative humidity. Also, on an annual basis, biases in all the variables are eliminated. The standard statistical indices of model performance computed after Kalman filtering are superior to those computed using only model output. Time series plots of bias and RMSE in model after Kalman filtering indicate the advantage of Kalman filtering.
由于网格分辨率、参数化方案、亚网格尺度现象处理、初始和边界条件数据以及插值技术等各种因素，数值天气预报模式在近地表大气参数预报中表现出系统误差。减少模型误差的方法之一是使用卡尔曼滤波算法，该算法递归地结合模型输出和观测值，使系统误差最小。在本研究中，利用卡尔曼滤波算法对2013年空气污染模型(the Air Pollution model, TAPM)的模型输出进行校正。修正后的变量为2 m空气温度、2 m相对湿度和10 m纬向风分量。在研究中使用了每小时在特罗姆贝站点获得的相同变量的观测结果。在本研究中可以看到，除了近地面空气温度和相对湿度外，经过卡尔曼滤波后的风速和风向都得到了较好的再现。此外，在每年的基础上，消除了所有变量的偏差。卡尔曼滤波后计算的模型性能的标准统计指标优于仅使用模型输出计算的统计指标。卡尔曼滤波后模型的偏差和RMSE的时间序列图说明了卡尔曼滤波的优点。
{"title":"Improvement in Near Surface NWP Model Output using Kalman Filtering Technique: A Case Study for Trombay Site","authors":"Roopashree Shrivastava, Indumathi Srinivasan Iyer, Rajendrakumar Balkrishna Oza","doi":"10.4401/ag-8919","DOIUrl":"https://doi.org/10.4401/ag-8919","url":null,"abstract":"Numerical Weather Prediction (NWP) models exhibit systematic errors in the forecast of near surface atmospheric parameters due to various factors like grid resolution, parameterization schemes, treatment of sub-grid scale phenomena, data for initial and boundary conditions and interpolation techniques. One of the methods for reduction in model errors is the use of Kalman filter algorithm which recursively combines model output and observations such that the systematic errors are minimized. In the present study, the Kalman filter algorithm is utilized for correction of model output from The Air Pollution Model (TAPM) for the year 2013. The variables corrected are 2-m air temperature, 2-m relative humidity and zonal and meridional wind components at 10-m. Hourly observations of the same variables available at Trombay site are used in the study. In the present study, it is seen that, both wind speed and wind direction are better reproduced after Kalman filtering, in addition to near surface air temperature and relative humidity. Also, on an annual basis, biases in all the variables are eliminated. The standard statistical indices of model performance computed after Kalman filtering are superior to those computed using only model output. Time series plots of bias and RMSE in model after Kalman filtering indicate the advantage of Kalman filtering.","PeriodicalId":50766,"journal":{"name":"Annals of Geophysics","volume":"52 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":"136233917","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Seismic horizon tracing is a key step in seismic data interpretation. At present, it mainly relies on manual interpretation to mark the layers within the region. The deficiency of manual interpretation lies in its low precision and efficiency, and it relies heavily on the experience of the interpreter. Aiming at the above problems, the author proposes an automatic horizon tracking algorithm with curvature constraint. The algorithm firstly determines the initial seed points of horizon tracking based on logging data, and then generates all seed points by tracing the direction of crossline. According to the seed point, track the horizon by the direction of the inline. The curvature of each horizon point is calculated in the direction of the crossline according to the tracked results. For the layer point that do not meet the ruling curvature threshold, they are traced again in the direction of the crossline, and finally the corrected tracking results are obtained. Through the test of actual data, this method has achieved good results.
{"title":"Automatic horizon tracking algorithm with curvature constraint","authors":"Jiji Zhou, Huiqun Xu, Ping Yang, Mengqiong Yang","doi":"10.4401/ag-8899","DOIUrl":"https://doi.org/10.4401/ag-8899","url":null,"abstract":"Seismic horizon tracing is a key step in seismic data interpretation. At present, it mainly relies on manual interpretation to mark the layers within the region. The deficiency of manual interpretation lies in its low precision and efficiency, and it relies heavily on the experience of the interpreter. Aiming at the above problems, the author proposes an automatic horizon tracking algorithm with curvature constraint. The algorithm firstly determines the initial seed points of horizon tracking based on logging data, and then generates all seed points by tracing the direction of crossline. According to the seed point, track the horizon by the direction of the inline. The curvature of each horizon point is calculated in the direction of the crossline according to the tracked results. For the layer point that do not meet the ruling curvature threshold, they are traced again in the direction of the crossline, and finally the corrected tracking results are obtained. Through the test of actual data, this method has achieved good results.","PeriodicalId":50766,"journal":{"name":"Annals of Geophysics","volume":"147 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74263119","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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