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.

scholarly journals Seismic hazard assessment of Iran

1999 ◽  
Vol 42 (6) ◽  
Author(s):  
B. Tavakoli ◽  
M. Ghafory-Ashtiany
Keyword(s):  
Seismic Hazard ◽  
Peak Ground Acceleration ◽  
Grid Point ◽  
Seismic Hazard Assessment ◽  
Earthquake Hazard ◽  
Seismic Source ◽  
Historical Earthquakes ◽  
Earthquake Insurance ◽  
Ground Acceleration ◽  
Seismic Source Models

The development of the new seismic hazard map of Iran is based on probabilistic seismic hazard computation using the historical earthquakes data, geology, tectonics, fault activity and seismic source models in Iran. These maps have been prepared to indicate the earthquake hazard of Iran in the form of iso-acceleration contour lines, and seismic hazard zoning, by using current probabilistic procedures. They display the probabilistic estimates of Peak Ground Acceleration (PGA) for the return periods of 75 and 475 years. The maps have been divided into intervals of 0.25 degrees in both latitudinal and longitudinal directions to calculate the peak ground acceleration values at each grid point and draw the seismic hazard curves. The results presented in this study will provide the basis for the preparation of seismic risk maps, the estimation of earthquake insurance premiums, and the preliminary site evaluation of critical facilities.

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>

Joint multidisciplinary study of the Saint-Sauveur–Donareo fault (lower Var valley, French Riviera): a contribution to seismic hazard assessment in the urban area of Nice

2011 ◽  
Vol 182 (4) ◽  
pp. 323-336 ◽  
Author(s):  
Christophe Larroque ◽  
Bertrand Delouis ◽  
Jean-Claude Hippolyte ◽  
Anne Deschamps ◽  
Thomas Lebourg ◽  
...  
Keyword(s):  
Seismic Hazard ◽  
Urban Areas ◽  
Regional Scale ◽  
Active Faults ◽  
Focal Depth ◽  
Strike Slip ◽  
Fault System ◽  
Geophysical Investigation ◽  
Lateral Strike Slip ◽  
North East

AbstractThe lower Var valley is the only large outcropping zone of Plio-Quaternary terrains throughout the southwestern Alps. In order to assess the seismic hazard for the Alps – Ligurian basin junction, we investigated this area to provide a record of earthquakes that have recently occurred near the city of Nice. Although no historical seismicity has been indicated for the lower Var valley, our main objective was to identify traces of recent faulting and to discuss the seismogenic potential of any active faults. We organized multidisciplinary observations as a microseismic investigation (the PASIS survey), with morphotectonic mapping and imagery, and subsurface geophysical investigations. The results of the PASIS dense recording survey were disappointing, as no present-day intense microseismic activity was recorded. From the morphotectonic investigation of the lower Var valley, we revealed several morphological anomalies, such as drainage perturbations and extended linear anomalies that are unrelated to the lithology. These anomalies strike mainly NE-SW, with the major Saint-Sauveur – Donareo lineament, clearly related to faulting of the Plio-Pleistocene sedimentary series. Sub-surface geophysical investigation (electrical resistivity tomography profiling) imaged these faults in the shallow crust, and together with the microtectonic data, allow us to propose the timing of recent faulting in this area. Normal and left-lateral strike-slip faulting occurred several times during the Pliocene. From fault-slip data, the last episode of faulting was left-lateral strike-slip and was related to a NNW-SSE direction of compression. This direction of compression is consistent with the present-day state of stress and the Saint-Sauveur–Donareo fault might have been reactivated several times as a left-lateral fault during the Quaternary. At a regional scale, in the Nice fold-and-thrust belt, these data lead to a reappraisal of the NE-SW structural trends as the major potentially active fault system. We propose that the Saint-Sauveur–Donareo fault belongs to a larger system of faults that runs from near Villeneuve-Loubet to the southwest to the Vésubie valley to the north-east. The question of a structural connection between the Vésubie – Mt Férion fault, the Saint-Sauveur–Donareo fault and its possible extension offshore through the northern Ligurian margin is discussed.The Saint-Sauveur–Donareo fault shows two en-échelon segments that extend for about 8 km. Taking into account the regional seismogenic depth (about 10 km), this fault could produce M ~6 earthquakes if activated entirely during one event. Although a moderate magnitude generally yields a moderate seismic hazard, we suggest that this contribution to the local seismic risk is high, taking into account the possible shallow focal depth and the high vulnerability of Nice and the surrounding urban areas.

scholarly journals SEISMIC HAZARD ESTIMATION IN STABLE CONTINENTAL REGIONS: DOES PSHA MEET THE NEEDS FOR MODERN ENGINEERING DESIGN IN AUSTRALIA?

2020 ◽  
Vol 53 (1) ◽  
pp. 22-36 ◽  
Author(s):  
Trevor I. Allen
Keyword(s):  
Seismic Hazard ◽  
Hazard Analysis ◽  
Ground Motions ◽  
Seismic Hazard Assessment ◽  
Earthquake Hazard ◽  
Exceedance Probability ◽  
Earthquake Catalogues ◽  
Seismic Safety ◽  
Seismic Demands ◽  
Almost All

Damaging earthquakes in Australia and other regions characterised by low seismicity are considered low probability but high consequence events. Uncertainties in modelling earthquake occurrence rates and ground motions for damaging earthquakes in these regions pose unique challenges to forecasting seismic hazard, including the use of this information as a reliable benchmark to improve seismic safety within our communities. Key challenges for assessing seismic hazards in these regions are explored, including: the completeness and continuity of earthquake catalogues; the identification and characterisation of neotectonic faults; the difficulties in characterising earthquake ground motions; the uncertainties in earthquake source modelling, and; the use of modern earthquake hazard information to support the development of future building provisions. Geoscience Australia recently released its 2018 National Seismic Hazard Assessment (NSHA18). Results from the NSHA18 indicate significantly lower seismic hazard across almost all Australian localities at the 1/500 annual exceedance probability level relative to the factors adopted for the current Australian Standard AS1170.4–2007 (R2018). These new hazard estimates have challenged notions of seismic hazard in Australia in terms of the recurrence of damaging ground motions. This raises the question of whether current practices in probabilistic seismic hazard analysis (PSHA) deliver the outcomes required to protect communities and infrastructure assets in low-seismicity regions, such as Australia. This manuscript explores a range of measures that could be undertaken to update and modernise the Australian earthquake loading standard, in the context of these modern seismic hazard estimates, including the use of alternate ground-motion exceedance probabilities for assigning seismic demands for ordinary-use structures. The estimation of seismic hazard at any location is an uncertain science, particularly in low-seismicity regions. However, as our knowledge of the physical characteristics of earthquakes improve, our estimates of the hazard will converge more closely to the actual – but unknowable – (time independent) hazard. Understanding the uncertainties in the estimation of seismic hazard is also of key importance, and new software and approaches allow hazard modellers to better understand and quantify this uncertainty. It is therefore prudent to regularly update the estimates of the seismic demands in our building codes using the best available evidence-based methods and models.

scholarly journals NDSHA - The New Paradigm for RSHA - An Updated Review

2021 ◽  
Vol 43 (2) ◽  
pp. 111-188
Author(s):  
J. Bela ◽  
G. F. Panza
Keyword(s):  
Seismic Hazard ◽  
Hazard Assessment ◽  
Time Scale ◽  
Seismic Hazard Assessment ◽  
Earthquake Hazard ◽  
New Paradigm ◽  
Range Space ◽  
Earthquake Physics ◽  
Space Scale ◽  
Main Shocks

A New Paradigm (data driven and not like the currently model driven) is needed for Reliable Seismic Hazard Assessment RSHA. Neo-Deterministic Seismic Hazard Assessment (NDSHA) integrates earthquake geology, earthquake science, and particularly earthquake physics to finally achieve a New (and needed) Paradigm for Reliable Seismic Hazard Assessment RSHA.Although observations from many recent destructive earthquakes have all confirmed the validity of NDSHA’s approach and application to earthquake hazard forecasting-nonetheless damaging earthquakes still cannot yet be predicted with a precision requirement consistent with issuing a red alert and evacuation order to protect civil populations. However, intermediate-term (time scale) and middle-range (space scale) predictions of main shocks above a pre-assigned threshold may be properly used for the implementation of low-key preventive safety actions, as recommended by UNESCO in 1997. Furthermore, a proper integration of both seismological and geodetic information has been shown to also reliably contribute to a reduction of the geographic extent of alarms and it therefore defines a New Paradigm for TimeDependent Hazard Scenarios: Intermediate-Term (time scale) and Narrow-Range (space scale) Earthquake Prediction. 

scholarly journals Neo-deterministic seismic hazard maps of Kosovo

2021 ◽  
Author(s):  
Enrico Brandmayr ◽  
Vaccari Franco ◽  
Romanelli Fabio ◽  
Vlahovic Gordana ◽  
Panza Giuliano Francesco
Keyword(s):  
Seismic Hazard ◽  
Ground Motion ◽  
Seismic Hazard Assessment ◽  
Active Regions ◽  
Earthquake Hazard ◽  
Earthquake Ground Motion ◽  
Hazard Maps ◽  
Source Information ◽  
Deterministic Seismic Hazard ◽  
Traditional Construction

Kosovo is one of the most seismically active regions in Europe, lying within the Alpine-Mediterranean tectonic belt. Historical records for the region show several catastrophic earthquakes with epicentral intensity IX (MCS). However, due to Kosovo’s high population density, high prevalence of traditional construction, and insufficient enforcement of building codes, Kosovo is vulnerable to earthquake damage. In this study, we present earthquake hazard maps for bedrock conditions in Kosovo based on the well-known Neo-deterministic Seismic Hazard Assessment (NDSHA) method. NDSHA relies upon the fundamental physics of wave generation and propagation in complex geologic structures to generate realistic time series, used as input for the computation of several ground motion parameters, integrating the available knowledge of seismic history, seismogenic zones and morphostructural nodes. In accordance with continuum mechanics, the tensor nature of earthquake ground motion is preserved, producing realistic signals using structural models obtained by tomographic inversion and earthquake source information readily available in literature. Our maps are generally consistent with the observed intensity IX (MCS) and suggest that, in some instances, intensity X could be reached.

scholarly journals Seismic hazard assessment in the Ibero-Maghreb region

1999 ◽  
Vol 42 (6) ◽  
Author(s):  
M. J. Jiménez ◽  
M. García-Fernández
Keyword(s):  
Seismic Hazard ◽  
Hazard Assessment ◽  
Seismic Hazard Assessment ◽  
Earthquake Hazard ◽  
Seismic Source ◽  
Common Procedure ◽  
Fruitful Cooperation ◽  
Seismic Hazard Map ◽  
First Time ◽  
Regional Earthquake

The contribution of the Ibero-Maghreb region to the global GSHAP map has been the result of a fruitful cooperation among the participants in the established Working Group including representatives from Algeria, Morocco, Portugal, Spain and Tunisia and coordinated by ICTJA-CSIC, Spain. For the first time, a map of regional seismic source zones is presented, and agreement on a common procedure for hazard computation in the region has been achieved. The computed Ibero-Maghreb seismic hazard map constitutes the first step towards a uniform hazard assessment for the region. Further joint regional efforts are still needed for earthquake hazard studies based on a homogeneous regional earthquake catalogue. Ongoing initiatives in relation to seismic hazard assessment in the Mediterranean should profit both from these results and the established cooperation among different groups in the region as well as contribute to future regional studies.

scholarly journals Probabilistic seismic hazard assessment in Greece – Part 3: Deaggregation

2010 ◽  
Vol 10 (1) ◽  
pp. 51-59 ◽  
Author(s):  
G-A. Tselentis ◽  
L. Danciu
Keyword(s):  
Seismic Hazard ◽  
Peak Ground Acceleration ◽  
Seismic Hazard Assessment ◽  
Earthquake Hazard ◽  
Earthquake Magnitude ◽  
Probabilistic Seismic Hazard Assessment ◽  
Hazard Maps ◽  
Ground Acceleration ◽  
Dense Grid ◽  
Motion Parameters

Abstract. The present third part of the study, concerning the evaluation of earthquake hazard in Greece in terms of various ground motion parameters, deals with the deaggregation of the obtained results The seismic hazard maps presented for peak ground acceleration and spectral acceleration at 0.2 s and 1.0 s, with 10% probability of exceedance in 50 years, were deaggregated in order to quantify the dominant scenario. There are three basic components of each dominant scenario: earthquake magnitude (M), source-to-site distance (R) and epsilon (ε). We present deaggregation maps of mean and mode values of M-R-ε triplet showing the contribution to hazard over a dense grid.

The Međimurje (Croatia) Earthquake of 1738

2020 ◽  
Vol 91 (2A) ◽  
pp. 1042-1056 ◽  
Author(s):  
Davorka Herak ◽  
Mladen Živčić ◽  
Iva Vrkić ◽  
Marijan Herak
Keyword(s):  
Seismic Hazard ◽  
Historical Data ◽  
Hanging Wall ◽  
Source Parameters ◽  
Focal Depth ◽  
Seismic Hazard Assessment ◽  
Maximum Intensity ◽  
Epicentral Intensity ◽  
Felt Area ◽  
The Town

Abstract The 30 March 1738 earthquake with an epicenter near Čakovec in Međimurje (Croatia) is the largest known earthquake in the low-seismicity area that includes northernmost Croatia, northeastern Slovenia, southeastern Austria, and southwestern Hungary. So far, it has attracted very little attention in the seismological communities of those countries. It is missing or has wrong source parameters in all of the relevant earthquake catalogs (including the Seismic Hazard Harmonization in Europe (SHARE) catalog, Stucchi et al., 2013), which may influence seismic hazard assessment in this part of Europe, most critically in the Međimurje region itself. We present contemporary historical data shedding some light on the effects that the earthquake had on settlements mostly in Međimurje, but also elsewhere in Croatia, Slovenia, and Hungary. We were able to assign intensities to 12 localities surrounding the epicenter and to resolve the confusion about its date of occurrence. The intensity points were inverted for the location of the macroseismic hypocenter and epicentral intensity (I0=7.9 MSK [Medvedev–Sponheuer–Karnik]). The epicenter is found to lie on the hanging wall of the reverse Čakovec fault, about 6 km from its surface trace, and 8 km north-northwest of the town of Čakovec. The rather small felt area for an earthquake of this maximum intensity implies a shallow macroseismic focal depth of 6 km. These values of intensity and depth correspond to a macroseismic magnitude of MLm 5.1.

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