scholarly journals Earthquake doublet revealed by multiple pulses in lacustrine seismo-turbidites

Geology ◽  
2021 ◽  
Author(s):  
Katleen Wils ◽  
Maxim Deprez ◽  
Catherine Kissel ◽  
Morgan Vervoort ◽  
Maarten Van Daele ◽  
...  
Keyword(s):  
Current Knowledge ◽  
Risk Mitigation ◽  
Flow Direction ◽  
Seismic Hazard Assessment ◽  
Turbidity Currents ◽  
Fault Behavior ◽  
West Sumatra ◽  
Multiple Pulses ◽  
Earthquake Sequences ◽  
Earthquake Doublet

Earthquake doublets have been described in fault systems around the world but have not yet been confidently resolved in paleoseismic records. Our current knowledge is limited to historical occurrences, preventing researchers from uncovering potential patterns or recognizing common fault behavior. Identification of prehistoric doublets is thus of crucial importance for adequate seismic hazard assessment and risk mitigation. We developed a new methodology to reveal the sedimentary imprint of earthquake doublets in lacustrine paleoseismic records based on flow direction analysis in multipulsed turbidites, because the delayed arrival of turbidity currents originating from the same source location demonstrates the occurrence of individual triggering mechanisms. As grains tend to align in the presence of a flow, we analyzed flow directions by determining the dominant orientation of elongated grains using a combination of grain size, paleomagnetism, and high-resolution X-ray computed tomography. This methodology was applied to a turbidite deposited by the 2007 CE earthquakes in West Sumatra (Mw 6.4 and 6.3, 2 h apart), and it provides the first unmistakable sedimentary evidence for an earthquake doublet. We argue that this methodology has great potential to be applied to multipulsed turbidites in various subaquatic paleoseismic records and can reveal the occurrence of unknown earthquake sequences.

Multiple pulses in lacustrine turbidites reveal earthquake doublets

2021 ◽  
Author(s):  
Katleen Wils ◽  
Maxim Deprez ◽  
Catherine Kissel ◽  
Morgan Vervoort ◽  
Maarten Van Daele ◽  
...  
Keyword(s):  
High Resolution ◽  
Seismic Hazard Assessment ◽  
Source Area ◽  
Natural Remanent Magnetization ◽  
Grain Size Analysis ◽  
Size Analysis ◽  
Turbidity Currents ◽  
West Sumatra ◽  
Multiple Pulses ◽  
Earthquake Sequences

<p>Earthquake doublets form a particular challenge for seismic hazard assessment and can provide insights into potentially characteristic fault behaviour. However, knowledge on this type of earthquake sequences is limited to information provided by historical archives as their identification in paleoseismic records is ambiguous. The continuous sedimentation records provided by lacustrine settings might be able to resolve closely-timed earthquakes, but confident identification of earthquake doublets has, up to now, not been made. To reveal the potential of these high-resolution records, we perform a detailed analysis of a multi-pulsed turbidite that has been identified in the sedimentary infill of Lake Singkarak and that was generated by the March 2007 West Sumatra earthquake doublet (i.e. two M<sub>w</sub>>6 shocks on adjacent fault segments at 2 hours apart). In order to distinguish non-synchronously generated pulses in this turbidite (different earthquake, same turbidite source area) from those that are potentially synchronously-generated (same earthquake, different turbidite source areas), we develop a new methodology that allows analysing paleoflow directions by using grain-size analysis, natural remanent magnetization measurements and high-resolution X-ray computed tomography. Combining these techniques allows us to reveal the absolute geographical orientation of elongated grains, which are considered to be deposited aligned to the dominant paleoflow direction. Application to the 2007 turbidite in Lake Singkarak allows identifying the presence of non-synchronously generated pulses, thus confirming that each earthquake in the 2007 West Sumatra doublet triggered separate turbidity currents in the lake. Our study thus underscores the invaluable sensitivity of lacustrine paleoseismic records and outlines a promising methodology to analyse previously-described multi-pulsed lacustrine turbidites to reveal the occurrence of, up to now, unknown earthquake doublets.</p>

scholarly journals The use of questionnaires for acquiring information on public perception of natural hazards and risk mitigation – a review of current knowledge and practice

2009 ◽  
Vol 9 (4) ◽  
pp. 1307-1325 ◽  
Author(s):  
D. K. Bird
Keyword(s):  
Natural Hazards ◽  
Public Perception ◽  
Current Knowledge ◽  
Risk Mitigation ◽  
Mode Of Delivery ◽  
Sampling Technique ◽  
Future Research ◽  
Delivery Mode ◽  
Management Procedures ◽  
Knowledge And Practice

Abstract. Questionnaires are popular and fundamental tools for acquiring information on public knowledge and perception of natural hazards. Questionnaires can provide valuable information to emergency management agencies for developing risk management procedures. Although many natural hazards researchers describe results generated from questionnaires, few explain the techniques used for their development and implementation. Methodological detail should include, as a minimum, response format (open/closed questions), mode of delivery, sampling technique, response rate and access to the questionnaire to allow reproduction of or comparison with similar studies. This article reviews current knowledge and practice for developing and implementing questionnaires. Key features include questionnaire design, delivery mode, sampling techniques and data analysis. In order to illustrate these aspects, a case study examines methods chosen for the development and implementation of questionnaires used to obtain information on knowledge and perception of volcanic hazards in a tourist region in southern Iceland. Face-to-face interviews highlighted certain issues with respect to question structure and sequence. Recommendations are made to overcome these problems before the questionnaires are applied in future research projects. In conclusion, basic steps that should be disclosed in the literature are provided as a checklist to ensure that reliable, replicable and valid results are produced from questionnaire based hazard knowledge and risk perception research.

scholarly journals Englacial seismic reflectivity: imaging crystal-orientation fabric in West Antarctica

2011 ◽  
Vol 57 (204) ◽  
pp. 639-650 ◽  
Author(s):  
Huw J. Horgan ◽  
Sridhar Anandakrishnan ◽  
Richard B. Alley ◽  
Peter G. Burkett ◽  
Leo E. Peters
Keyword(s):  
Crystal Orientation ◽  
Seismic Velocity ◽  
Current Knowledge ◽  
Flow Direction ◽  
Ice Sheet ◽  
West Antarctica ◽  
Amplitude Analysis ◽  
Abrupt Changes ◽  
Seismic Reflectivity ◽  
Ice Sheet Dynamics

AbstractAbrupt changes in crystal-orientation fabric (COF), and therefore viscosity, are observed near the base of the ice sheet throughout West Antarctica. We report on active-source seismic observations from WAIS Divide, mid-stream and downstream on Thwaites Glacier, and the onset region of Bindschadler Ice Stream. These data reveal a prevalence of englacial seismic reflectivity in the bottom quarter of the ice sheet. The observed seismic reflectivity is complex but largely bed-conformable, with long-spatial-wavelength features observed in the flow direction and short-wavelength features observed across flow. A correspondence of englacial structures with bed features is also observed. We determine the origin of the reflectivity to be abrupt changes in the COF of ice, based on the following: (1) observations of englacial reflectivity are consistent with current knowledge of COF within ice sheets, (2) englacial reflectivity caused by COF contrasts requires the simplest genesis, especially at ice divides, and (3) amplitude analysis shows that the observed englacial reflectivity can be explained by contrasts in seismic velocity due to COF changes. We note that the downstream increase in the quantity and complexity of observations indicates that direct observations of COF at ice divides likely underestimate the role that fabric plays in ice-sheet dynamics.

Optimizing barrier placement for lava flow hazard and risk mitigation

2020 ◽  
Author(s):  
Giuseppe Bilotta ◽  
Annalisa Cappello ◽  
Veronica Centorrino ◽  
Claudia Corradino ◽  
Gaetana Ganci ◽  
...  
Keyword(s):  
Lava Flow ◽  
Risk Mitigation ◽  
Flow Direction ◽  
Economic Loss ◽  
Lava Flows ◽  
Mount Etna ◽  
Area Of Interest ◽  
Lava Flow Hazard ◽  
Mitigation Action ◽  
The Impact

<p>Mitigating hazards when lava flows threaten infrastructure is one of the most challenging fields of volcanology, and has an immediate and practical impact on society. Lava flow hazard is determined by the probability of inundation, and essentially controlled by the topography of the area of interest. The most common actions of intervention for lava flow hazard mitigation are therefore the construction of artificial barriers and ditches that can control the flow direction and advancement speed. Estimating the effect a barrier or ditch can have on lava flow paths is non-trivial, but numerical modelling can provide a powerful tool by simulating the eruptive scenario and thus assess the effectiveness of the mitigation action. We present a numerical method for the design of optimal artificial barriers, in terms of location and geometric features, aimed at minimizing the impact of lava flows based on the spatial distribution of exposed elements. First, an exposure analysis collects information about elements at risk from different datasets: population per municipality, distribution of buildings, infrastructure, routes, gas and electricity networks, and land use; numerical simulations are used to compute the probability for these elements to be inundated by lava flows from a number of possible eruptive scenarios  (hazard assessment) and computing the associated economic loss and potential destruction of key facilities (risk assessment). We then generate several intervention scenarios, defined by the location, orientation and geometry (width, length, thickness and even shape) of multiple barriers, and compute the corresponding variation in economic loss. Optimality of the barrier placement is thus considered as a minimization problem for the economic loss, controlled by the barrier placement and constrained by the associated costs. We demonstrate the operation of this system by using a retrospective analysis of some recent effusive eruptions at Mount Etna, Sicily.</p>

scholarly journals 25,000 Years Long Seismic Cycle in a Slow Deforming Continental Region of Mongolia

2021 ◽  
Author(s):  
Laurent Bollinger ◽  
Yann Klinger ◽  
Steven Forman ◽  
Odonbaatar Chimed ◽  
Amgalan Bayasgalan ◽  
...  
Keyword(s):  
Seismic Hazard ◽  
Active Faults ◽  
Ground Surface ◽  
Slip Rate ◽  
Seismic Hazard Assessment ◽  
Return Time ◽  
Fault Behavior ◽  
Seismogenic Structures ◽  
Cumulative Deformation ◽  
Large Earthquakes

Abstract The spatial distribution of large earthquakes in Slowly Deforming Continental Regions (SDCR) is poorly documented and, thus, has often been deemed to be random. Unlike in high strain regions, where seismic activity concentrates cyclically along major active faults, earthquakes in SDCR may seem to occur more erratically in space and time. This questions classical fault behavior models, posing paramount issues for seismic hazard assessment. Here, we investigate the M7, 1967, Mogod earthquake in Mongolia, a region recognized as a SDCR. Despite the absence of visible cumulative deformation at the ground surface, we found evidence for at least 3 surface rupturing earthquakes during the last 50,000 years, associated to a slip-rate of 0,06 ± 0,01 mm/yr. These results show that in SDCR, like in faster deforming regions, deformation localizes on specific structures. However, the excessive length of return time for large earthquakes along these structures makes it more difficult to recognize earthquake series, and could conversely lead to the misconception that in SDCR earthquakes would be randomly located. Thus, our result emphasizes the need for systematic appraisal of the potential seismogenic structures in SDCR in order to lower the uncertainties associated with the seismogenic sources in seismic hazard models.

scholarly journals Supplemental Material: Earthquake doublet revealed by multiple pulses in lacustrine seismo-turbidites

2021 ◽  
Author(s):  
Katleen Wils ◽  
et al.
Keyword(s):  
Sediment Cores ◽  
Multiple Pulses ◽  
Earthquake Doublet

Detailed information on the studied sediment cores and methods.<br>

scholarly journals 25,000 Years long seismic cycle in a slow deforming continental region of Mongolia

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Laurent Bollinger ◽  
Yann Klinger ◽  
Steven L. Forman ◽  
Odonbaatar Chimed ◽  
Amgalan Bayasgalan ◽  
...  
Keyword(s):  
Seismic Hazard ◽  
Active Faults ◽  
Ground Surface ◽  
Slip Rate ◽  
Seismic Hazard Assessment ◽  
Return Time ◽  
Fault Behavior ◽  
Seismogenic Structures ◽  
Cumulative Deformation ◽  
Large Earthquakes

AbstractThe spatial distribution of large earthquakes in slowly deforming continental regions (SDCR) is poorly documented and, thus, has often been deemed to be random. Unlike in high strain regions, where seismic activity concentrates along major active faults, earthquakes in SDCR may seem to occur more erratically in space and time. This questions classical fault behavior models, posing paramount issues for seismic hazard assessment. Here, we investigate the M7, 1967, Mogod earthquake in Mongolia, a region recognized as a SDCR. Despite the absence of visible cumulative deformation at the ground surface, we found evidence for at least 3 surface rupturing earthquakes during the last 50,000 years, associated with a slip-rate of 0.06 ± 0.01 mm/year. These results show that in SDCR, like in faster deforming regions, deformation localizes on specific structures. However, the excessive length of return time for large earthquakes along these structures makes it more difficult to recognize earthquake series, and could conversely lead to the misconception that in SDCR earthquakes would be randomly located. Thus, our result emphasizes the need for systematic appraisal of the potential seismogenic structures in SDCR in order to lower the uncertainties associated with the seismogenic sources in seismic hazard models.

scholarly journals Quantitatively deciphering paleostrain from digital outcrops model and its application in the eastern Tian Shan, China

2020 ◽  
Author(s):  
Xin Wang ◽  
Feng Gao
Keyword(s):  
Quantitative Methods ◽  
Risk Mitigation ◽  
Strain Tensor ◽  
Seismic Hazard Assessment ◽  
Local Strain ◽  
Tectonic Stress ◽  
Fault Slip ◽  
High Quality ◽  
Fracture Development ◽  
Tian Shan

&lt;p&gt;The knowledge of the strain/stress field evolution in time is important to seismic hazard assessment and risk mitigation, and is fundamental to the understanding of the earth dynamic system. Based on the principle that past tectonic stress should have left traces in the rocks, geologists have been trying to determine the paleostress history from evidence found in rocks for decades. Recent development of techniques for automatic extraction of fracture surfaces from digital outcrop models and estimation of historical shear deformation on rock fractures provide an efficient way of quantitatively acquiring large amount of high quality fracture/fault slip data (direction and sense of slip occurs on the fault plane) from outcrops. So unlike traditional paleostress inversion methods whose data is manually collected in the field, this high quality fracture/fault slip data provide an opportunity to develop fully automatic and quantitative methods for deciphering paleostrain. In this study, for slip on each fracture, the corresponding local strain tensor is calculated, then the local strain tensors are grouped into populations corresponding to far-field strain events and local strain events using a clustering analysis technique. The applications on outcrops in the eastern Tian Shan area give a clear picture of the paleostrain variation over space and time, and also throw light on the relationship between paleostrain, fracture development and the distribution of shear displacements in a thrusting environment.&lt;/p&gt;

scholarly journals SARS-CoV-2 and Implantation Window: Gene Expression Mapping of Human Endometrium and Preimplantation Embryo

Life ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1378
Author(s):  
Delphine Haouzi ◽  
Frida Entezami ◽  
Edward Tuaillon ◽  
Anna Gala ◽  
Alice Ferrières-Hoa ◽  
...  
Keyword(s):  
Gene Expression ◽  
Current Knowledge ◽  
Risk Mitigation ◽  
Expression Profiles ◽  
Female Genital Tract ◽  
Renin Angiotensin System ◽  
Preimplantation Embryos ◽  
Entire Cohort ◽  
Implantation Window ◽  
The Impact

Understanding whether SARS-CoV-2 could infect cells and tissues handled during ART is crucial for risk mitigation, especially during the implantation window when either endometrial biopsies are often practiced for endometrial receptivity assessment or embryo transfer is performed. To address this question, this review analyzed current knowledge of the field and retrospectively examined the gene expression profiles of SARS-CoV-2-associated receptors and proteases in a cohort of ART candidates using our previous Affymetrix microarray data. Human endometrial tissue under natural and controlled ovarian stimulation cycles and preimplantation embryos were analyzed. A focus was particularly drawn on the renin-angiotensin system, which plays a prominent role in the virus infection, and we compared the gene expression levels of receptors and proteases related to SARS-CoV-2 infection in the samples. High prevalence of genes related to the ACE2 pathway during both cycle phases and mainly during the mid-secretory phase for ACE2 were reported. The impact of COS protocols on endometrial gene expression profile of SARS-CoV-2-associated receptors and proteases is minimal, suggesting no additional potential risks during stimulated ART procedure. In blastocysts, ACE2, BSG, CTSL, CTSA and FURIN were detectable in the entire cohort at high expression level. Specimens from female genital tract should be considered as potential targets for SARS-CoV-2, especially during the implantation window.

scholarly journals Supplemental Material: Earthquake doublet revealed by multiple pulses in lacustrine seismo-turbidites

2021 ◽  
Author(s):  
Katleen Wils ◽  
et al.
Keyword(s):  
Sediment Cores ◽  
Multiple Pulses ◽  
Earthquake Doublet

Detailed information on the studied sediment cores and methods.<br>

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