scholarly journals Integration of historical, archaeoseismic and paleoseismological data for the reconstruction of the early seismic history in Messina Strait (south Italy): the 1st and 4th centuries AD earthquakes

2014 ◽  
Vol 57 (1) ◽  
Author(s):  
Maria Serafina Barbano ◽  
Viviana Castelli ◽  
Daniela Pantosti ◽  
Claudia Pirrotta
Keyword(s):  
Historical Data ◽  
Seismic Source ◽  
Seismic Sources ◽  
Tsunami Deposits ◽  
Damage Area ◽  
South Italy ◽  
Messina Strait ◽  
Historical Accounts ◽  
Crete Earthquake ◽  
Northeastern Sicily

<p>Historical accounts, archaeoseismic and paleoseismological evidence allowed us to reappraise two earthquakes affecting northeastern Sicily and southern Calabria in the 1st (probably between 14 and 37) and 4th (likely between 361 and 363) centuries AD, to obtain a better reconstruction of their effects and to reconsider their sources.The 1st century event damaged the area from Oppido (Calabria) to Tindari (Sicily), roughly that of the February 6, 1783 Calabria earthquake. The similitude of these earthquakes is further stressed by the fact that they generated tsunamis, as recorded by historical data and by the tsunami deposits found at Capo Peloro, the oldest dated 0-125 AD, the youngest linked to the 1783 event. These earthquakes could be related to the same Calabria seismic source: the Scilla fault. Northeastern Sicily and southern Calabria were also damaged by one or more earthquakes in the 4th century AD and several towns were rebuilt/restored at that time. The hit area roughly coincides with that of the Messina 1908 earthquake suggesting similar seismic sources for the events. However, because close in time, historical descriptions of the 4th century Sicilian earthquake were mixed with those of the 365 Crete earthquake that generated a basin-wide tsunami most likely reaching also the Sicilian coasts. Reevaluating location, size, damage area and tsunamigenic potential of these two earthquakes of the 1st and 4th centuries AD is relevant for reassessing the seismogenic and tsunamigenic potential of the faults around the Messina Strait and the seismic hazard of the affected areas.</p>

Exploiting wind-turbine noise for seismic imaging and monitoring

2020 ◽  
Author(s):  
Elmer Ruigrok ◽  
Lisanne Jagt ◽  
Britt van der Vleut
Keyword(s):  
Wind Turbine ◽  
Seismic Noise ◽  
Seismic Source ◽  
Seismic Network ◽  
Seismic Sources ◽  
The Novel ◽  
Wind Turbine Noise ◽  
Cost Reductions ◽  
Cost Efficient ◽  
Subsurface Monitoring

&lt;p&gt;Wind turbines (WTs) have proven to be an increasingly cost-efficient source of sustainable energy. With further cost reductions and growth of environmental awareness, the amount and size of WTs will further expand. In the seismic literature, WTs have mainly been considered a threat rather than an opportunity. WTs act as infrasound and seismic sources, whose wavefield might overwhelm signal from earthquakes. Rather than focusing on the detrimental effects, we embrace the WT revolution and focus on the novel possibilities of the WT seismic source. We show detailed characteristics of this source using recordings over the Groningen seismic network. We further show examples of using the WT seismic noise for extracting medium parameters. Moreover, we exploit the repeatable nature of the source for subsurface monitoring.&lt;/p&gt;

Using historical accounts to assess the occurrence and distribution of small cetaceans in a poorly known area

2010 ◽  
Vol 90 (8) ◽  
pp. 1583-1588 ◽  
Author(s):  
Cristina Brito ◽  
Nina Vieira
Keyword(s):  
Historical Data ◽  
Historical Science ◽  
13Th Century ◽  
Historical Sources ◽  
Baleen Whales ◽  
Delphinus Delphis ◽  
Large Numbers ◽  
Alternative Sources ◽  
Historical Accounts ◽  
Common Dolphins

Historical science may play an important role in helping understanding and shaping the future of the world's oceans and to comprehend present day effects and conditions. Regarding cetaceans, historical accounts may be extremely useful to add new data to their occurrence and distribution in poorly studied regions. In Portugal, historical sources indicate that toninhas (possibly common dolphins Delphinus delphis) were observed since the 13th Century and were captured in large numbers during the late 19th and 20th Centuries. Historical occurrences given by naturalists and scientific surveys conducted by biologists indicate their regular presence with particular preference for certain areas. Also, recent observations of opportunity resulted in the same kind of accounts. Between 1976 and 1978, a study on captured cetaceans along the Portuguese shore found at fish markets was conducted and resulted in a total count of 45 cetaceans. Most captures were of small cetaceans (87% common dolphins), even though four baleen whales were registered. These cetacean captures were part of a local non-industrial fishery, as they were not the main target, but rather opportunistic catches or even by-catches of other fisheries. Delphinids were not protected by law at the time and were caught with hand harpoons or accidentally drowned in fish nets, sometimes sold at major fish markets such as Sesimbra, Peniche and Póvoa de Varzim. In geographical areas where recent cetacean sightings are rare and information is sparse, such as Portugal, it becomes important to take advantage of alternative sources of data. Our contribution towards the compilation of relevant historical and ‘forgotten’ science such as old natural observations, whaling data and observations of opportunity stresses the relevance of using historical data to access past occurrence and distribution of cetaceans.

scholarly journals SEISMIC SOURCES AND MAIN SEISMIC FAULTS IN THE AEGEAN AND SURROUNDING AREA

2017 ◽  
Vol 43 (4) ◽  
pp. 2026 ◽  
Author(s):  
G.F. Karakaisis ◽  
C.B. Papazachos ◽  
E.M. Scordilis
Keyword(s):  
Seismic Source ◽  
Seismic Sources ◽  
Surrounding Area ◽  
Aegean Area ◽  
Instrumental Data ◽  
Seismogenic Layer ◽  
Horizontal Dimension ◽  
Basic Parameters

A seismic source is defined, in the present work, as the part of the seismogenic layer of theearth’s crust with a circular horizontal dimension (E, R), where E is the epicenter of the largestearthquake (mainshock) ever occurred in this seismic source and radius equal to the half faultlength of this largest earthquake (R=L/2). In addition to foreshocks and aftershocks othersmaller mainshocks occur in other smaller faults of this source or in parts of the main fault.All available historical and instrumental data concerning strong (M³6.0) shallow (h≤60 km) andintermediate depth (60km<h≤100km) shocks which occurred in the Aegean area between 464B.C. and 2008 are used in the present work in an attempt to identify the seismic sources in thisarea, as well as to determine the basic parameters of the largest fault in each source. A particularprocedure is followed to identify 155 seismic sources in this area and determine thebasic parameters of the largest fault in each source. Declustering has been also performed todefine mainshocks in the Aegean area and the completeness of this mainshock catalogue hasbeen determined. Results are summarized in table (1).

scholarly journals Seismic and Geodetic Crustal Moment-Rates Comparison: New Insights on the Seismic Hazard of Egypt

2021 ◽  
Vol 11 (17) ◽  
pp. 7836
Author(s):  
Rashad Sawires ◽  
José A. Peláez ◽  
Federica Sparacino ◽  
Ali M. Radwan ◽  
Mohamed Rashwan ◽  
...  
Keyword(s):  
Active Regions ◽  
Seismic Source ◽  
Satellite System ◽  
Dead Sea ◽  
Fault System ◽  
Gulf Of Aqaba ◽  
Seismic Sources ◽  
Earthquake Catalog ◽  
Focal Mechanism Solutions ◽  
Rate Ratios

A comparative analysis of geodetic versus seismic moment-rate estimations makes it possible to distinguish between seismic and aseismic deformation, define the style of deformation, and also to reveal potential seismic gaps. This analysis has been performed for Egypt where the present-day tectonics and seismicity result from the long-lasting interaction between the Nubian, Eurasian, and Arabian plates. The data used comprises all available geological and tectonic information, an updated Poissonian earthquake catalog (2200 B.C.–2020 A.D.) including historical and instrumental datasets, a focal-mechanism solutions catalog (1951–2019), and crustal geodetic strains from Global Navigation Satellite System (GNSS) data. The studied region was divided into ten (EG-01 to EG-10) crustal seismic sources based mainly on seismicity, focal mechanisms, and geodetic strain characteristics. The delimited seismic sources cover the Gulf of Aqaba–Dead Sea Transform Fault system, the Gulf of Suez­–Red Sea Rift, besides some potential seismic active regions along the Nile River and its delta. For each seismic source, the estimation of seismic and geodetic moment-rates has been performed. Although the obtained results cannot be considered to be definitive, among the delimited sources, four of them (EG-05, EG-06, EG-08, and EG-10) are characterized by low seismic-geodetic moment-rate ratios (<20%), reflecting a prevailing aseismic behavior. Intermediate moment-rate ratios (from 20% to 60%) have been obtained in four additional zones (EG-01, EG-04, EG-07, and EG-09), evidencing how the seismicity accounts for a minor to a moderate fraction of the total deformational budget. In the other two sources (EG-02 and EG-03), high seismic-geodetic moment-rates ratios (>60%) have been observed, reflecting a fully seismic deformation.

The Wolfspar experience with low-frequency seismic source field data: Motivation, processing, and implications

2022 ◽  
Vol 41 (1) ◽  
pp. 9-18
Author(s):  
Andrew Brenders ◽  
Joe Dellinger ◽  
Imtiaz Ahmed ◽  
Esteban Díaz ◽  
Mariana Gherasim ◽  
...  
Keyword(s):  
Gulf Of Mexico ◽  
Seismic Data ◽  
Field Data ◽  
Model Building ◽  
Low Frequency ◽  
Seismic Source ◽  
Velocity Model ◽  
Seismic Sources ◽  
Velocity Model Building ◽  
Air Gun

The promise of fully automatic full-waveform inversion (FWI) — a (seismic) data-driven velocity model building process — has proven elusive in complex geologic settings, with impactful examples using field data unavailable until recently. In 2015, success with FWI at the Atlantis Field in the U.S. Gulf of Mexico demonstrated that semiautomatic velocity model building is possible, but it also raised the question of what more might be possible if seismic data tailor-made for FWI were available (e.g., with increased source-receiver offsets and bespoke low-frequency seismic sources). Motivated by the initial value case for FWI in settings such as the Gulf of Mexico, beginning in 2007 and continuing into 2021 BP designed, built, and field tested Wolfspar, an ultralow-frequency seismic source designed to produce seismic data tailor-made for FWI. A 3D field trial of Wolfspar was conducted over the Mad Dog Field in the Gulf of Mexico in 2017–2018. Low-frequency source (LFS) data were shot on a sparse grid (280 m inline, 2 to 4 km crossline) and recorded into ocean-bottom nodes simultaneously with air gun sources shooting on a conventional dense grid (50 m inline, 50 m crossline). Using the LFS data with FWI to improve the velocity model for imaging produced only incremental uplift in the subsalt image of the reservoir, albeit with image improvements at depths greater than 25,000 ft (approximately 7620 m). To better understand this, reprocessing and further analyses were conducted. We found that (1) the LFS achieved its design signal-to-noise ratio (S/N) goals over its frequency range; (2) the wave-extrapolation and imaging operators built into FWI and migration are very effective at suppressing low-frequency noise, so that densely sampled air gun data with a low S/N can still produce useable model updates with low frequencies; and (3) data density becomes less important at wider offsets. These results may have significant implications for future acquisition designs with low-frequency seismic sources going forward.

Rayleigh-Wave Multicomponent Crosscorrelation-Based Estimation of Phase Velocities and Ambient Seismic Source Distributions

2020 ◽  
Author(s):  
Zongbo Xu
Keyword(s):  
Rayleigh Waves ◽  
Field Data ◽  
Seismic Source ◽  
Coda Waves ◽  
Seismic Sources ◽  
Subsurface Structure ◽  
Phase Velocities ◽  
Wave Phase ◽  
Multicomponent Data ◽  
Seismic Wavefield

One uses seismic interferometry (SI) to recover Green's functions (i.e. impulse response) from ambient seismic recordings and estimate surface-wave phase velocities to investigate subsurface structure. This method has been commonly used in the last 20 years because this method only utilizes ambient seismic recordings from seismic stations/sensors and does not rely on traditional seismic sources (e.g. earthquakes or active sources). SI assumes that the ambient seismic wavefield is isotropic, but this assumption is rarely met in practice. We demonstrate that, with linear-array spatial sampling of an anisotropic ambient seismic wavefield, SI provides a better estimate of Rayleigh-wave phase velocities than another commonly used ambient seismic method, the refraction microtremor (ReMi) method. However, even SI does not work in some extreme cases, such as when the out-of-line sources are stronger than the inline sources. This is because the recovered Green's functions and surface-wave phase velocity estimations from SI are biased due to the anisotropic wavefield. Thus, we propose to use multicomponent data to mitigate this bias. The multicomponent data are vertical (Z) and radial (R) components, where the R direction is parallel to a line or great circle path between two sensors. The multicomponent data can deal with the extreme anisotropic source cases, because the R component is more sensitive to the in-line sources than the out-of-line sources, while the Z component possesses a constant sensitivity to sources in all directions. Estimation of source distributions (i.e. locations and strengths) can aid correction of the bias in SI results, as well as enable the study of natural ambient seismic sources (e.g. microseism). We use multicomponent seismic data to estimate ambient seismic source distributions using full-waveform inversion. We demonstrate that the multicomponent data can better constrain the inversion than only the Z component data, due to the different source sensitivities between the Z and R components. When applying the inversion to field data, we propose a general workflow which is applicable for different field scales and includes vertical and multicomponent data. We demonstrate the workflow with a field data example from the CO2 degassing in Harstouˇsov, Czech Republic. We also apply the workflow to the seismic recordings in Antarctica during February 2010 and estimate the primary microseism source distributions. The SI results include both direct and coda waves. While using the direct waves in investigating subsurface structure and estimating source distributions, one can utilize the coda waves to monitor small changes in the subsurface. The coda waves include multiply-scattered body and surface waves. The two types of waves possess different spatial sensitivities to subsurface changes and interact each other through scattering. We present a Monte Carlo simulation to demonstrate the interaction in an elastic homogeneous media. In the simulation, we incorporate the scattering process between body and Rayleigh waves and the eigenfunctions of Rayleigh waves. This is a first step towards a complete modelling of multiply-scattered body and surface waves in elastic media.

On the use of a seismic sensor as a seismic source

Geophysics ◽  
2013 ◽  
Vol 78 (5) ◽  
pp. A39-A43
Author(s):  
David F. Halliday ◽  
Taiwo Fawumi ◽  
Johan O. A. Robertsson ◽  
Ed Kragh
Keyword(s):  
Surface Wave ◽  
Surface Waves ◽  
Group Velocity ◽  
Seismic Source ◽  
Body Waves ◽  
Seismic Sources ◽  
Wave Group ◽  
Seismic Sensors ◽  
Voltage Signal ◽  
Seismic Wavefield

We investigated the use of seismic sensors as small seismic sources. A voltage signal is applied to a geophone that forces the mass within the geophone to move. The movement of the mass generates a seismic wavefield that was recorded with an array of geophones operating in the conventional sense. We observed higher-frequency (25 Hz and above) surface and body waves propagating from the geophone source at offsets of 10 s of meters. We further found that the surface waves emitted from geophone sources can be used to generate a surface-wave group velocity map. We discuss potential developments and future applications.

Field comparison of shallow seismic sources

Geophysics ◽  
1986 ◽  
Vol 51 (11) ◽  
pp. 2067-2092 ◽  
Author(s):  
R. D. Miller ◽  
S. E. Pullan ◽  
J. S. Waldner ◽  
F. P. Haeni
Keyword(s):  
Water Table ◽  
Seismic Source ◽  
Single Site ◽  
Seismic Sources ◽  
Shallow Seismic ◽  
Site Characteristics ◽  
Amplitude Spectra ◽  
Different Characteristics ◽  
Magnitude Difference ◽  
Selection Of

Choosing a seismic source for a shallow reflection survey can be the most pivotal decision for the engineering geophysicist. The intent of this paper is to present data that will assist in selection of a shallow seismic source best meeting the goals within the constraints of specific projects, particularly in areas where the water table is near the surface. The data were collected (and displayed as seismograms and amplitude spectra) for 15 different shallow seismic sources in October, 1985, at a single site in New Jersey; they show the different characteristics of each source. Considering the almost three orders of magnitude difference in total source energy between the largest and smallest source, we chose a display format that presented the data as objectively as possible, while still allowing direct source‐to‐source comparisons. Two strong reflections at about 100 and 130 ms probably mark the top and bottom of a clay unit 80 m below the surface at this site. Our previous work and that of our colleagues suggests that, given a specific set of site characteristics, any source could dominate the comparison categories addressed here.

scholarly journals Body force equivalents for stress-drop seismic sources

1976 ◽  
Vol 66 (6) ◽  
pp. 1801-1804
Author(s):  
Robert J. Geller
Keyword(s):  
Principal Stress ◽  
Stress Drop ◽  
Body Force ◽  
Seismic Source ◽  
Seismic Sources ◽  
Body Forces ◽  
Independent Functions ◽  
Double Couple ◽  
Stress Drops

abstract The equivalent body forces for a stress-drop seismic source are found. When the isotropic stress drop and one of the three principal stress drops are zero, then the equivalent body forces are the same double couple without moment which would result from a shear dislocation. In general however, all six stress-drop components must be specified as independent functions of time.

scholarly journals Introducing noisi: a Python tool for ambient noise cross-correlation modeling and noise source inversion

Solid Earth ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 1597-1615
Author(s):  
Laura Ermert ◽  
Jonas Igel ◽  
Korbinian Sager ◽  
Eléonore Stutzmann ◽  
Tarje Nissen-Meyer ◽  
...  
Keyword(s):  
Wave Propagation ◽  
Noise Source ◽  
Seismic Source ◽  
Seismic Wave Propagation ◽  
Seismic Sources ◽  
Source Inversion ◽  
Cross Correlations ◽  
Forward And Inverse Modeling ◽  
Noise Cross Correlation ◽  
Spatially Varying

Abstract. We introduce the open-source tool noisi for the forward and inverse modeling of ambient seismic cross-correlations with spatially varying source spectra. It utilizes pre-computed databases of Green's functions to represent seismic wave propagation between ambient seismic sources and seismic receivers, which can be obtained from existing repositories or imported from the output of wave propagation solvers. The tool was built with the aim of studying ambient seismic sources while accounting for realistic wave propagation effects. Furthermore, it may be used to guide the interpretation of ambient seismic auto- and cross-correlations, which have become preeminent seismological observables, in light of nonuniform ambient seismic sources. Written in the Python language, it is accessible for both usage and further development and efficient enough to conduct ambient seismic source inversions for realistic scenarios. Here, we introduce the concept and implementation of the tool, compare its model output to cross-correlations computed with SPECFEM3D_globe, and demonstrate its capabilities on selected use cases: a comparison of observed cross-correlations of the Earth's hum to a forward model based on hum sources from oceanographic models and a synthetic noise source inversion using full waveforms and signal energy asymmetry.

Sign in / Sign up

Export Citation Format

Share Document