Cortical deformation in the Aguacaliente-Navarro fault system (Central Valley, Costa Rica) from Geodetic data (GNSS and InSAR)

2020 ◽  
Author(s):  
Juan José Portela Fernández ◽  
Alejandra Staller Vázquez ◽  
Marta Béjar Pizarro
Keyword(s):  
Costa Rica ◽  
Seismic Hazard ◽  
Seismic Hazard Assessment ◽  
Central Valley ◽  
Fault System ◽  
Moderate Seismicity ◽  
Cumulative Strain ◽  
Gnss Data ◽  
The City ◽  
Turrialba Volcano

<p>The Central Valley, Costa Rica, is subject to moderate seismicity, related to the Central Costa Rica Deformation Belt: a region with diffuse deformation, where Caribbean, Cocos and Nazca Plates, as well as the Panama Micro-plate, interact.  The Eastern part of the valley is dominated by the Aguacaliente-Navarro fault system. The city of Cartago was destroyed by an earthquake Ms 6.4 in 1910, associated with the rupture of the Aguacaliente fault. Volcanic unrest –mainly in Turrialba Volcano, with recent activity reported- is present in the area, thus resulting in a very complex interaction zone, where seismic hazard studies are crucial.</p><p>In this context, we process GNSS observations from five different campaigns -2012, 2014, 2016, 2018 and 2020- in 13 stations in the area, in order to estimate their Caribbean-fixed velocities, hence the regional cumulative strain. Additionally, we use both InSAR and GNSS data to measure volcanic deformation, aiming to refine the computed velocities by removing volcanic deformation from the tectonic signal.</p><p>The refined velocities allow us to asses a more precise cumulative strain for the Aguacaliente-Navarro fault system, which is useful to improve seismic hazard assessment in Cartago, one of the most important cities in the region.</p>

scholarly journals The use of Monte Carlo simulations for seismic hazard assessment in the U.K.

2000 ◽  
Vol 43 (1) ◽  
Author(s):  
R. M. W. Musson
Keyword(s):  
Monte Carlo ◽  
Seismic Hazard ◽  
Hazard Assessment ◽  
Seismic Hazard Assessment ◽  
Probabilistic Seismic Hazard Assessment ◽  
Logic Tree ◽  
The United Kingdom ◽  
The Monte Carlo Method ◽  
Moderate Seismicity ◽  
Seismicity Model

The input required for a seismic hazard study using conventional Probabilistic Seismic Hazard assessment (PSHA) methods can also be used for probabilistic analysis of hazard using Monte Carlo simulation methods. This technique is very flexible, and seems to be under-represented in the literature. It is very easy to modify the form of the seismicity model used, for example, to introduce non-Poissonian behaviour, without extensive reprogramming. Uncertainty in input parameters can also be modelled very flexibly - for example, by the use of a standard deviation rather than by the discrete branches of a logic tree. In addition (and this advantage is perhaps not as trivial as it may sound) the simplicity of the method means that its principles can be grasped by the layman, which is useful when results have to be explained to people outside the seismological/engineering communities, such as planners and politicians. In this paper, some examples of the Monte Carlo method in action are shown in the context of a low to moderate seismicity area: the United Kingdom.

scholarly journals Extraction of Land Information, Future Landscape Changes and Seismic Hazard Assessment: A Case Study of Tabriz, Iran

Sensors ◽  
2020 ◽  
Vol 20 (24) ◽  
pp. 7010
Author(s):  
Ayub Mohammadi ◽  
Sadra Karimzadeh ◽  
Khalil Valizadeh Kamran ◽  
Masashi Matsuoka
Keyword(s):  
Markov Chain ◽  
Land Cover ◽  
Seismic Hazard ◽  
Hazard Assessment ◽  
Seismic Hazard Assessment ◽  
The Future ◽  
Future Potential ◽  
Potential Landscape ◽  
The City ◽  
Future Landscape

Exact land cover inventory data should be extracted for future landscape prediction and seismic hazard assessment. This paper presents a comprehensive study towards the sustainable development of Tabriz City (NW Iran) including land cover change detection, future potential landscape, seismic hazard assessment and municipal performance evaluation. Landsat data using maximum likelihood (ML) and Markov chain algorithms were used to evaluate changes in land cover in the study area. The urbanization pattern taking place in the city was also studied via synthetic aperture radar (SAR) data of Sentinel-1 ground range detected (GRD) and single look complex (SLC). The age of buildings was extracted by using built-up areas of all classified maps. The logistic regression (LR) model was used for creating a seismic hazard assessment map. From the results, it can be concluded that the land cover (especially built-up areas) has seen considerable changes from 1989 to 2020. The overall accuracy (OA) values of the produced maps for the years 1989, 2005, 2011 and 2020 are 96%, 96%, 93% and 94%, respectively. The future potential landscape of the city showed that the land cover prediction by using the Markov chain model provided a promising finding. Four images of 1989, 2005, 2011 and 2020, were employed for built-up areas’ land information trends, from which it was indicated that most of the built-up areas had been constructed before 2011. The seismic hazard assessment map indicated that municipal zones of 1 and 9 were the least susceptible areas to an earthquake; conversely, municipal zones of 4, 6, 7 and 8 were located in the most susceptible regions to an earthquake in the future. More findings showed that municipal zones 1 and 4 demonstrated the best and worst performance among all zones, respectively.

scholarly journals Fault System-Based Probabilistic Seismic Hazard Assessment of a Moderate Seismicity Region: The Eastern Betics Shear Zone (SE Spain)

2020 ◽  
Vol 8 ◽  
Author(s):  
Octavi Gómez-Novell ◽  
Julián García-Mayordomo ◽  
María Ortuño ◽  
Eulàlia Masana ◽  
Thomas Chartier
Keyword(s):  
Seismic Hazard ◽  
Return Period ◽  
Fault System ◽  
Probabilistic Seismic Hazard ◽  
Se Spain ◽  
Slip Rates ◽  
Area Source ◽  
Moderate Seismicity ◽  
Background Seismicity ◽  
Hazard Levels

Including faults as seismogenic sources in probabilistic seismic hazard assessments (PSHA) has turned into a common practice as knowledge of active faults is improving. Moreover, the occurrence of earthquakes in multi-fault ruptures has evidenced the need to understand faults as interacting systems rather than independent sources. We present a PSHA for the Southeastern Spain obtained by including the faults of a moderate seismicity region, the Eastern Betics Shear Zone (EBSZ) in SE Spain, as the main seismogenic sources in two separate source models, one considering background seismicity. In contrast with previous studies in Spain, earthquake occurrence of the EBSZ system is modeled considering different hypotheses of multi-fault ruptures at the whole fault system scale and weighted in a logic tree. We compare the hazard levels with those from an area source PSHA and a previous fault-based approach. The results show a clear control of the EBSZ faults in the seismic hazard for all return periods, increasing drastically the hazard levels in the regions close to the fault traces and influencing up to 20 km farther with respect to the area source PSHA. The seismic hazard is dependent on the fault slip rates as peak ground accelerations and territorial extension of the fault influence appear higher around the Alhama de Murcia and Carboneras faults, while lower slip rate faults (Palomares Fault) show minor contribution to the hazard. For the return period of 475 years and near-fault locations, our models are more consistent with the ground motion values reached in the 2011 Mw 5.2 Lorca event than the building code or national seismic hazard map, which suggest that our fault system-based model performs more accurate estimations for this return period. Fault data, mainly slip rates, and its uncertainties have a clear impact on the seismic hazard and, for some faults, the lack of detailed paleoseismic studies can compromise the reliability of the hazard estimations. This, together with epistemic uncertainties concerning the background seismicity, are key discussion points in the present study, having an impact on further research and aiming to serve as a case example for other low-to-moderate seismicity regions worldwide.

scholarly journals Approach for combining fault and area sources in seismic hazard assessment: application in south-eastern Spain

2018 ◽  
Vol 18 (11) ◽  
pp. 2809-2823 ◽  
Author(s):  
Alicia Rivas-Medina ◽  
Belen Benito ◽  
Jorge Miguel Gaspar-Escribano
Keyword(s):  
Seismic Hazard ◽  
Hazard Assessment ◽  
Methodological Approach ◽  
Hybrid Approach ◽  
Seismic Hazard Assessment ◽  
Source Model ◽  
Zone Model ◽  
Essential Difference ◽  
Seismic Potential ◽  
Moderate Seismicity

Abstract. This paper presents a methodological approach to seismic hazard assessment based on a hybrid source model composed of faults as independent entities and zones containing residual seismicity. The seismic potential of both types of sources is derived from different data: for the zones, the recurrence model is estimated from the seismic catalogue. For fault sources, it is inferred from slip rates derived from palaeoseismicity and GNSS (Global Navigation Satellite System) measurements. Distributing the seismic potential associated with each source is a key question when considering hybrid zone and fault models, and this is normally resolved using one of two possible alternatives: (1) considering a characteristic earthquake model for the fault and assigning the remaining magnitudes to the zone, or (2) establishing a cut-off magnitude, Mc, above which the seisms are assigned to the fault and below which they are considered to have occurred in the zone. This paper presents an approach to distributing seismic potential between zones and faults without restricting the magnitudes for each type of source, precluding the need to establish cut-off Mc values beforehand. This is the essential difference between our approach and other approaches that have been applied previously. The proposed approach is applied in southern Spain, a region of low-to-moderate seismicity where faults move slowly. The results obtained are contrasted with the results of a seismic hazard method based exclusively on the zone model. Using the hybrid approach, acceleration values show a concentration of expected accelerations around fault traces, which is not appreciated in the classic approach using only zones.

Fault-Plane Determination of the 4 January 2020 Offshore Pearl River Delta Earthquake and Its Implication for Seismic Hazard Assessment

2021 ◽  
Author(s):  
Han Chen ◽  
Xiaohui He ◽  
Hongfeng Yang ◽  
Jiangyang Zhang
Keyword(s):  
Seismic Hazard ◽  
Focal Depth ◽  
River Estuary ◽  
Correlation Method ◽  
Primary Source ◽  
Seismic Hazard Assessment ◽  
Earthquake Hazard ◽  
Fault System ◽  
Pearl River ◽  
Rupture Directivity

Abstract On 4 January 2020, an ML 3.5 earthquake occurred in the Pearl River Estuary (PRE) and was felt at a distance of more than 200 km. According to the China Earthquake Networks Center, this event has been the only M>3 earthquake within the PRE since 1900. The Guangdong–Hong Kong–Macau Bay Area (GHMBA) surrounding the PRE is one of China’s most critical financial circles, and coastal earthquake hazard has become an increasing concern. Investigating the source parameter and causative fault of this earthquake is helpful for seismic hazard estimation and mitigation in the GHMBA. In this study, we first determined the focal mechanism of the mainshock using the cut-and-paste method. We then used the sliding-window cross-correlation method to detect foreshocks and aftershocks before relocating the earthquakes. Finally, we conducted forward modeling to retrieve the rupture directivity of the mainshock, using waveforms of one aftershock as empirical Green’s functions. The results demonstrate that this earthquake was an Mw 3.7 strike-slip event, with a focal depth of 10 km. The rupture direction of the mainshock was 78°, consistent with the northeast-east-trending fault system in the region. The identified source fault confirmed a seismogenic segment of the northeast-east-trending fault system in the PRE, which is the primary source of seismic hazard in the area.

Seismic hazard assessment of the city of Hamedan and its vicinity, west of Iran

2012 ◽  
Vol 63 (2) ◽  
pp. 1025-1038 ◽  
Author(s):  
Mohammad Hossein Ghobadi ◽  
Davood Fereidooni
Keyword(s):  
Seismic Hazard ◽  
Hazard Assessment ◽  
Seismic Hazard Assessment ◽  
The City

scholarly journals Rapid response to the Mw 4.9 earthquake of November 11, 2019 in Le Teil, Lower Rhône Valley, France

2020 ◽  
Author(s):  
Cécile Cornou ◽  
Jean-Paul Ampuero ◽  
Coralie aubert ◽  
Laurence Audin ◽  
Stéphane Baize ◽  
...  
Keyword(s):  
Focal Depth ◽  
Seismic Hazard Assessment ◽  
Normal Fault ◽  
Field Evaluation ◽  
Fault System ◽  
Seismic Unit ◽  
Epicentral Area ◽  
Massif Central ◽  
Moderate Seismicity ◽  
Rhone Valley

On November 11, 2019, a Mw 4.9 earthquake hit the region close to Montelimar (lower Rhône Valley, France), on the eastern margin of the Massif Central close to the external part of the Alps. Occuring in a moderate seismicity area, this earthquake is remarkable for its very shallow focal depth (between 1 and 3 km), its magnitude,  and the moderate to large damages it produced in several villages. InSAR interferograms indicated a shallow rupture about 4 km long reaching the surface and the reactivation of the ancient NE-SW La Rouviere normal fault in reverse faulting in agreement with the present-day E-W compressional tectonics. The peculiarity of this earthquake together with a poor coverage of the epicentral region by permanent seismological and geodetic stations triggered the mobilisation of the French post-seismic unit and the broad French scientific community from various institutions, with the deployment of geophysical instruments (seismological and geodesic stations),  geological field surveys, and field evaluation of the intensity of the earthquake. Within 7 days after the mainshock, 47 seismological stations were deployed in the epicentral area to improve the Le Teil aftershocks locations relative to the French permanent seismological network (RESIF), monitor the temporal and spatial evolution of microearthquakes close to the fault plane and temporal evolution of the seismic response of 3 damaged historical buildings, and to study suspected site effects and their influence in the distribution of seismic damage. This seismological dataset, completed by data owned by different institutions, was integrated in a homogeneous archive and distributed through FDSN web services by the RESIF data center. This dataset, together with observations of surface rupture evidences, geologic, geodetic and satellite data, will help to unravel the causes and rupture mechanism of this earthquake, and contribute to account in seismic hazard assessment for earthquakes along the major regional Cévenne fault system in a context of present-day compressional tectonics.

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