💧🌏 Greg CocksNov 23, 2024
Earthquake Hazard Uncertainties Improved Using Precariously Balanced Rocks
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https://doi.org/10.1029/2020AV000182 <-- shared paper
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#GIS #spatial #mapping #spatialanalysis #geomorphometry #probabilistic #seismichazard #analysis #PSHA #groundmotion #earthquake #risk #hazard #naturalhazard #quantitative #fault #faulting #geology #engineeringgeology #empirical #balancedrocks #PBR #California #cosmogenic #10Be #dating #model #modeling #hazardmodel #probability #infrastructure #cost #economics
💧🌏 Greg CocksNov 17, 2024
The 2023 US 50-State National Seismic Hazard Model - Overview And Implications
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https://www.usgs.gov/programs/earthquake-hazards/science/2023-national-seismic-hazard-model-whats-shaking <-- USGS technical article
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https://doi.org/10.1177/87552930231215428 <-- shared paper
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#GIS #spatial #mapping #earthquake #seismichazard #risk #hazard #shakemap #cost #economics #geology #engineeringgeology #hazardmodel #model #modeling #seismicity #faultruptures #groundmotions #probabilistic #probability #geostatistics #engineering #planning #management #mitigation #NSHM #forecast #infrastructure #publicsafety #hazardassessment #fault #faulting #structuralgeology #intensity #mercalli #buildingcode #design #publicpolicy #shakemap #engineeringrisk #future
@USGS @FEMA
The 2023 National Seismic Hazard Model – What's Shaking? | U.S. Geological Survey

No one can predict earthquakes. But existing faults and past earthquakes give us information about future earthquakes, and geology tells us how the ground shakes during an earthquake.

WeAreSeismicaOct 22, 2024

Using seismic noise and Horizontal-to-Vertical Spectral Ratios, Ávila-Barrientos et al. find a great dispersion of VS30 results in Baja California, Mexico, consistent with the heterogeneities between The Mexicali Valley and the Peninsular Ranges:

https://seismica.library.mcgill.ca/article/view/1151

#mexico #bajacalifornia #seismichazard #Seismology #EarthquakeScience #peerreviewed #DiamondOpenAccess #Earthquake #OpenAccess #OpenScience

Seismic site conditions of RESNOM network

The Northwest Seismic Network of Mexico (RESNOM) is operated by personnel from the Center for Scientific Research and Higher Education of Ensenada, Baja California (CICESE), which supervises station installation, improvement, and maintenance. We employed seismic noise and the Horizontal to Vertical Spectral Ratio (HVSR) method to determine, for each station, the following site condition parameters: the depth of the rock layer (Heng_bed), and the geotechnical parameter VS30, obtained from 1D shear wave velocity models. Other parameters as the fundamental frequency (f0) and the average amplitude at the fundamental frequency (A0) were also estimated. Our results show clear differences between the values obtained for the Mexicali Valley and the Peninsular ranges regions. The VS30 obtained for stations of the Mexicali Valley region falls in the range from 173 m/s to 535 m/s, while for the Peninsular Ranges region is between 213 m/s and 958 m/s. Regarding the Heng_bed parameter, the values are similar between both regions, from 23 m to 850 m for the Peninsular and from 42 m to 926 m for the Mexicali Valley. Additionally, from the VS30 values, we propose the site classification according to the U.S. National Earthquake Hazards Reduction Program (NEHRP).

Seismica
💧🌏 Greg CocksAug 2, 2024
Imaging Below The Surface Reveals One Of Los Angeles's Webs Of Faults
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https://phys.org/news/2024-07-imaging-surface-reveals-los-angeles.html <-- shared technical article
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https://doi.org/10.1029/2023AV001155 <-- shared paper
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#GIS #spatial #mapping #remotesensing #sonar #model #modeling #engineeringgeology #geophysics #geology #earthquake #fault #faulting
#risk #hazard #spatialanalysis #LosAngles #California #USA #slip #PalosVerdesFault #seismology #seismic #earthquakeengineering #displacement #offset #fluids #water #hydrology #propogation #seismichazard #naturalhazards
Imaging below the surface reveals one of Los Angeles's webs of faults

A major fault is often surrounded by a web of secondary faults created as the forces that cause slip deform nearby rocks. This damage zone can act as a record of fault activity, but what we can learn from it—such as how the fault may behave during future earthquakes—has not been fully explored.

Phys.org
💧🌏 Greg CocksMay 9, 2024
Increasing Fault Slip Rates Within The Corinth Rift, Greece - A Rapidly Localising Active Rift Fault Network
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https://doi.org/10.1016/j.epsl.2024.118716 <-- shared paper
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#GIS #spatial #mapping #geology #structuralgeology #CorinthRift #Riftevolution #Faultnetworkevolution #Borderfaultsystem #Seismichazard #IODPexpedition381 #seismic #stratigraphy #fault #faulting #earthquake #IODP #Greece #spatialanalysis #spatiotemporal #model #modeling #rifting #borehole #sample #risk #hazard #engineeringgeology #seismichazard
WeAreSeismicaMay 6, 2024

A new passive OBS dataset acquired in the Red Sea by Parisi et al. reveals that microseisms are frequently generated locally and that there could be new volcanoes or hydrothermal vents waiting to be discovered!

More here: https://doi.org/10.26443/seismica.v3i1.729

#seismology #EarthquakeScience #peerreviewed #OBS #RedSea #seismichazard #DiamondOpenAccess #Earthquake #OpenAccess #OpenScience

The First Network of Ocean Bottom Seismometers in the Red Sea to Investigate the Zabargad Fracture Zone

In the last decades, the slow-spreading Red Sea rift has been the objective of several geophysical investigations to study the extension of the oceanic crust, the thickness of the sedimentary cover, and the formation of transform faults. However, local seismology datasets are still lacking despite their potential to contribute to the understanding of the tectonic evolution of the Red Sea. The Zabargad Fracture Zone is located in the Northern Red Sea and significantly offsets the rift axis to the East. Thus, it is considered a key tectonic element to understand better the formation of the Red Sea rift. To fill the gap in the dataset availability, we deployed the first passive seismic network in the Red Sea, within the Zabargad Fracture Zone. This network included 12 Lobster OBSs from the DEPAS pool, 2 OBS developed and deployed by Fugro, and 4 portable seismic land stations deployed on islands and onshore on the Saudi Arabian coast. Our data-quality analysis confirms that the head-buoy cable free to strum, as well as other additional elements of the DEPAS OBSs, generate seismic noise at frequencies $>$ 10 Hz. However, the Fugro OBSs show high-frequency disturbances even if they lack vibrating elements. Comparison between land and OBS stations reveals that noise between 1 and 10 Hz is due to ocean-generated seismic noise, and not due to resonance of the OBS elements. We also found that waveforms of teleseismic earthquakes recorded by the Fugro OBSs, islands, and onshore stations have comparable signal-to-noise ratios. Instead, differences in signal-to-noise ratio for local earthquakes are affected more by site and path effects than instrument settings.

Seismica
💧🌏 Greg CocksFeb 27, 2024
Deep Structure of Siletzia in the Puget Lowland - Imaging an Obducted Plateau and Accretionary Thrust Belt With Potential Fields
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https://doi.org/10.1029/2022TC007720 <--shared paper
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[I used to live, work as an engineering geologist and scuba dive in Puget Sound & beyond – including on the expressions of the Seattle Fault…]
#GIS #spatial #mapping #engineeringgeology #Seattle #pugetsound #washingtonstate #fault #faulting #earthquake #tsunami #structuralgeology #PNW #plateboundary #crustal #tectonics #cascadia #forearc #siletzia #seismic #seismichazard #geologichazard #risk #hazard #glacial #sediments #pugetlowland #model #modeling #remotesensing #magnetic #aeromagnetism #gravity #folding #thrust #geologicmapping #geology #seismology #accretionary #obduction #spatialanalysis #spatiotemporal #seattlefault #earthquakehazard #earthquakeengineering
💧🌏 Greg CocksJan 18, 2024
New Map Shows Where Damaging Earthquakes Are Most Likely To Occur In US
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https://phys.org/news/2024-01-earthquakes.html <-- shared technical article
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https://doi.org/10.1177/87552930231215428 <-- shared paper
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#GIS #spatial #mapping #earthquakes #USA #risk #hazard #evaluation #USGS #model #modeling #spatialanalysis #SeismicHazard #NSHM #geology #engineeringgeology #geologichistory #fault #faulting #tectonics #engineers #structures #codes #buildingcodes #buildingdesign #quake #seismicdesign #assessment #publicsafety #planning #requlations #engineering
@USGS
New map shows where damaging earthquakes are most likely to occur in US 

Nearly 75% of the U.S. could experience damaging earthquake shaking, according to a recent U.S. Geological Survey-led team of more than 50 scientists and engineers.

Phys.org
Doug BostromOct 16, 2023

"The potency of earthquakes in each country, we define as the sum of fatalities reported divided by the number of earthquakes that generated the associated disasters. Thus, the potency measures the size of the disaster generated by an average fatal earthquake in each country."

Unexpected?

"The leaders in the list of potency are Haiti, Azerbaijan, Syria and Israel, all with potencies above 20,000 fatalities per average earthquake."

#SeismicHazard
#OpenAccess
https://link.springer.com/article/10.1007/s11069-022-05627-x

Earthquake fatalities and potency - Natural Hazards

We have compiled a new catalogue of earthquake fatalities for the world, covering the period 856 BC to March 2022, listing 2795 reports. We estimate that the reporting of fatal earthquakes is complete for events with more than 16 fatalities since 1927. The total number of fatalities recorded is 8,336,526. 117 countries have reported at least one earthquake with one fatality or more. 77 and 52 countries have reported more than 100 and 1000 earthquake fatalities, respectively. Caution has to be exercised in estimating what earthquake disasters are in store for a given country because the 95 year period of high quality recording is about an order of magnitude shorter than return times of great earthquakes. Nevertheless, we introduce the earthquake potency for a country, defined as the sum of recorded fatalities divided by the number of earthquakes that it took to accumulate them, which equals the average earthquake disaster size in a given country, in units of fatalities per event. Potency is listed based on all known fatal earthquakes and also based on those since 1927. Both lists have their shortcomings, but provide estimates of what size of future earthquake disaster is likely in store for a particular country. For rescue purposes, it is important to realize that small earthquake, M 5 ± 0.5, can cause significant numbers of fatalities.

SpringerLink
WeAreSeismicaJul 8, 2023

Evangelidis et al. image the western edge of the Aegean Shear Zone using the South Evia 2022-2023 Seismic Sequence.

They identify the activation of a NW-SE fault structure, emphasizing the urgency for better seismic network coverage in the region.

Read: https://seismica.library.mcgill.ca/article/view/1032

#seismology #earthquake #Aegean #faultstructure #strikeslip #seismicnetwork #machinelearning #seismichazard

Imaging the Western Edge of the Aegean Shear Zone: The South Evia 2022-2023 Seismic Sequence

This report presents the 2022-2023 South Evia island seismic sequence, in the western Aegean sea. An automated workflow, undergoing testing for efficient observatory monitoring in the wake of dense aftershock sequences, was employed to enhance the seismic catalog. It includes a deep-learning phase picker, absolute and relative hypocenter relocation, and moment tensor automatic calculations. The relocated catalog reveals a concentration of earthquake epicenters in a narrow NW-SE zone, with sinistral strike-slip fault movement. The findings of the study indicate the occurrence of an asymmetric rupture within conjugate fault structures in the western Aegean region. These fault structures, although not necessarily both active, play a significant role in marking the transition from dextral (SW-NE) to sinistral (NW-SE) strike-slip ruptures, connecting the Aegean shear zone with normal faulting in mainland Greece. The South Evia 2022-2023 seismic sequence has revealed the activation of this NW-SE strike-slip structure, contrary to previous assumptions of low seismicity in the region. The study highlights the importance of reassessing seismic hazard maps and considering the potential activation of similar zones further south in the future. It also emphasizes the need for the expansion and the densification of seismic networks within the Aegean.

Seismica