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  • Articles  (53)
  • Seismological Society of America  (43)
  • Seismological Society of America (SSA)  (7)
  • Springer  (2)
  • Blackwell Publishing Ltd  (1)
  • Washington, DC : United States Gov. Print. Off.
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  • 1
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    High-Frequency Attenuation in the Lake Van Region, Eastern Turkey (2015)
    Seismological Society of America
    Details
    Publication Date: 2021-06-25
    Description: We provide a complete description of the characteristics of excitation and attenuation of the ground motion in the Lake Van region (eastern Turkey) using a data set that includes three-component seismograms from the 23 October 2011 Mw 7.1 Van earthquake, as well as its aftershocks. Regional attenuation and source scaling are parameterized to describe the observed ground motions as a function of distance, frequency, and magnitude. Peak ground velocities are measured in selected narrow frequency bands from 0.25 to 12.5 Hz; observed peaks are regressed to define a piecewise linear regional attenu- ation function, a set of excitation terms, and a set of site response terms. Results are modeled through random vibration theory (see Cartwright and Longuet-Higgins, 1956). In the log–log space, the regional crustal attenuation is modeled with a bilinear geo- metrical spreading g r characterized by a crossover distance at 40 km: g r ∝ r^−1 fits our results at short distances (r 〈 40 km), whereas g r ∝ r^−0.3 is better at larger distances (40 〈 r 〈 200 km). A frequency-dependent quality factor, Q f =100( f/fref)^ 0:43 (in which fref 1.0 Hz), is coupled to the geometrical spreading. Because of the inherent trade-off of the excitation/attenuation parameters (Δσ and κ), their specific values strongly depend on the choice made for the stress drop of the smaller earthquakes. After choosing a Brune stress drop ΔσBrune 4 MPa at Mw 3:5, we were able to define (1) an effective high frequency, distance- and mag- nitude-independent roll-off spectral parameter, κeff = 0:03 s and (2) a size-dependent stress-drop parameter, which increases with moment magnitude, from ΔσBrune 4 MPa at Mw 3.5 to ΔσBrune 20 MPa at Mw 7.1. The set of parameters mentioned here may be used in order to predict the earthquake-induced ground motions expected from future earthquakes in the region surrounding Lake Van.
    Description: Published
    Description: 4T. Fisica dei terremoti e scenari cosismici
    Description: JCR Journal
    Description: open
    Keywords: Earthquake-induced ground motion, Lake Van, Crustal attenuation ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
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    Ground-motion scaling in the Western Alps (2007)
    Springer
    Details
    Publication Date: 2017-04-04
    Description: In order to empirically obtain the scaling relationships for the high-frequency ground motion in the Western Alps (NW Italy), regressions are carried out on more than 7500 seismograms from 957 regional earthquakes. The waveforms were selected from the database of 6 three-component stations of the RSNI (Regional Seismic network of Northwestern Italy). The events,MW ranging between 1.2 and 4.8, were recorded within a hypocentral distance of 200 km during the time period: 1996–2001. The peak ground velocities are measured in selected narrow-frequency bands, between 0.5 and 14 Hz. Results are presented in terms of a regional attenuation function for the vertical ground motion, a set of vertical excitation terms at the reference station STV2 (hard-rock), and a set of site terms (vertical and horizontal), all relative to the vertical component of station STV2. The regional propagation of the ground motion is modeled after quantifying the expected duration of the seismic motion as a function of frequency and hypocentral distance. A simple functional form is used to take into account both the geometrical and the anelastic attenuation: a multi-variable grid search yielded a quality factor Q( f ) = 310 f 0.20, together with a quadri-linear geometrical spreading at low frequency. A simpler, bilinear geometrical spreading seems to be more appropriate at higher frequencies (f 〉 1.0 Hz). Excitation terms are matched by using a Brune spectral model with variable, magnitude-dependent stress drop: at Mw 4.8, we used σ = 50MPa. A regional distanceindependent attenuation parameter is obtained (κ0 = 0.012 s) by modelling the average spectral decay at high frequency of small earthquakes. In order to predict the absolute levels of ground shaking in the region, the excitation/attenuation model is used through the Random Vibration Theory (RVT) with a stochastic point-source model. The expected peak-ground accelerations (PGA) are compared with the ones derived by Ambraseys et al. (1996) for the Mediterranean region and by Sabetta and Pugliese (1996) for the Italian territory.
    Description: Published
    Description: 315-333
    Description: JCR Journal
    Description: reserved
    Keywords: Attenuation ; Ground motion ; Western Alps ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
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    A regional ground motion excitation/attenuation model for the San Francisco region (2007)
    Seismological Society of America
    Details
    Publication Date: 2017-04-04
    Description: By using small-to-moderate-sized earthquakes located within ~200 km of San Francisco, we characterize the scaling of the ground motions for frequencies ranging between 0.25 and 20 Hz, obtaining results for geometric spreading, Q(f), and site parameters using the methods of Mayeda et al. (2005) and Malagnini et al. (2004). The results of the analysis show that, throughout the Bay Area, the average regional attenuation of the ground motion can be modeled with a bilinear geometric spreading function with a 30 km crossover distance, coupled to an anelastic function exp(-pi*f*r/V*Q(f)) , where: Q(f)=180f^0.42. A body-wave geometric spreading, g(r)= r^-1.0, is used at short hypocentral distances (r 〈 30 km), whereas g(r)= r^-0.6 fits the attenuation of the spectral amplitudes at hypocentral distances beyond the crossover. The frequency-dependent site effects at 12 of the Berkeley Digital Seismic Network (BDSN) stations were evaluated in an absolute sense using coda-derived source spectra. Our results show: i) the absolute site response for frequencies ranging between 0.3 Hz and 2.0 Hz correlate with independent estimates of the local magnitude residuals (dML) for each of the stations; ii) moment-magnitudes (MW) derived from our path and site-corrected spectra are in excellent agreement with those independently derived using full-waveform modeling as well as coda-derived source spectra; iii) we use our weak-motion-based relationships to predict motions region wide for the Loma Prieta earthquake, well above the maximum magnitude spanned by our data set, on a completely different set of stations. Results compare well with measurements taken at specific NEHRP site classes; iv) an empirical, magnitude-dependent scaling was necessary for the Brune stress parameter in order to match the large magnitude spectral accelerations and peak ground velocities with our weak-motion-based model.
    Description: Published
    Description: 843-862
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: JCR Journal
    Description: partially_open
    Keywords: ground motion San Francisco site effects ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 4
    Electronic Resource
    Electronic Resource
    HYDROLOGY OF A DRAINED FORESTED POCOSIN WATERSHED (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Water Resources Association 33 (1997), S. 0 
    Details
    ISSN: 1752-1688
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: : In order to assess the effects. of silvicultural and drainage practices on water quality it is necessary to understand their impacts on hydrology. The hydrology of a 340 ha artificially drained forested watershed in eastern North Carolina was studied for a five-year period (1988–92). Effects of soils, beds and changes in vegetation on water table depth, evapotranspiration (ET) and drainage outflows were analyzed. Total annual outflows from the watershed varied from 29 percent of the rainfall during the driest year (1990) when mostly mature trees were present to as much as 53 percent during a year of normal rainfall (1992) after about a third of the trees were harvested. Annual ET from the watershed, calculated as the difference between annual rainfall and outflow, varied from 76 percent of the calculated potential ET for a dry year to as much as 99 percent for a wet year. Average estimated ET was 58 percent of rainfall for the five-year period. Flow rates per unit area were consistently higher from a smaller harvested block (Block B - 82 ha) of the watershed than from the watershed as a whole. This is likely due to time lags, as drainage water flows through the ditch-canal network in the watershed, and to timber harvesting of the smaller gaged block.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1752-1688.1997.tb03530.x
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    Paper (German National Licenses)
    Fulltext
  • 5
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    Two Deep Earthquakes in Wyoming (2015)
    Seismological Society of America (SSA)
    Details
    Publication Date: 2015-05-05
    Print ISSN: 0895-0695
    Electronic ISSN: 1938-2057
    Topics: Geosciences
    Published by Seismological Society of America (SSA)
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  • 6
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    Computer Programs in Seismology: An Evolving Tool for Instruction and Research (2013)
    Seismological Society of America (SSA)
    Details
    Publication Date: 2013-10-25
    Print ISSN: 0895-0695
    Electronic ISSN: 1938-2057
    Topics: Geosciences
    Published by Seismological Society of America (SSA)
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  • 7
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    Monitoring the Earthquake Source Process in North America (2011)
    Seismological Society of America (SSA)
    Details
    Publication Date: 2011-12-01
    Description: With the implementation of the USGS National Earthquake Information Center Prompt Assessment of Global Earthquakes for Response system (PAGER), rapid determination of earthquake moment magnitude is essential, especially for earthquakes that are felt within the contiguous United States. We report an implementation of moment tensor processing for application to broad, seismically active areas of North America. This effort focuses on the selection of regional crustal velocity models, codification of data quality tests, and the development of procedures for rapid computation of the seismic moment tensor. We systematically apply these techniques to earthquakes with reported magnitude greater than 3.5 in continental North America that are not associated with a tectonic plate boundary.Using the 0.02–0.10 Hz passband, we can usually determine, with few exceptions, moment tensor solutions for earthquakes with Mw as small as 3.7. The threshold is significantly influenced by the density of stations, the location of the earthquake relative to the seismic stations and, of course, the signal-to-noise ratio. With the existing permanent broadband stations in North America operated for rapid earthquake response, the seismic moment tensor of most earthquakes that are Mw 4 or larger can be routinely computed. As expected the nonuniform spatial pattern of these solutions reflects the seismicity pattern. However, the orientation of the direction of maximum compressive stress and the predominant style of faulting is spatially coherent across large regions of the continent.
    Print ISSN: 0037-1106
    Electronic ISSN: 1943-3573
    Topics: Geosciences , Physics
    Published by Seismological Society of America (SSA)
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  • 8
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    An Investigation of MbLg Versus Mw for Eastern North America (2014)
    Seismological Society of America (SSA)
    Details
    Publication Date: 2014-05-04
    Print ISSN: 0895-0695
    Electronic ISSN: 1938-2057
    Topics: Geosciences
    Published by Seismological Society of America (SSA)
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  • 9
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    Rapid Estimates of the Source Time Function and Mw using Empirical Green's Function Deconvolution (2014)
    Seismological Society of America (SSA)
    Details
    Publication Date: 2014-08-08
    Description: The U.S. Geological Survey National Earthquake Information Center (NEIC) uses a variety of classical network-averaged magnitudes (e.g., m b and M s ) and waveform modeling procedures to determine the moment magnitude ( M w ) of an earthquake from teleseismic observations. Initial magnitude estimates are often inaccurate because of poor azimuthal control (sampling of the focal sphere) and/or intrinsic limitation of each method to a specific range of event size. To provide faster and more accurate estimates of the moment magnitude, source duration, and source complexity, NEIC is exploring the use of a variation of the empirical Green’s function (EGF) deconvolution procedure. This approach uses a predicted focal mechanism derived from the Global Centroid Moment Tensor Catalog to compute teleseismic P -wave synthetic seismograms, which are then deconvolved from observed P and SH waveforms to determine station-specific M w , source time function, and a network-averaged M w . Our EGF approach is validated using broadband waveforms from 246 earthquakes in the magnitude range M w  6.0–9.1. Within approximately 13 min of earthquake origin time, our procedure using teleseismic P waves only computes an M w that lies within ±0.25 of the final W -phase M w in the magnitude range 6–8. Using later arriving teleseismic SH phases results in an M w that lies within ±0.12 of the W -phase M w . For magnitude 8 or larger earthquakes, we underestimated the moment magnitude by up to 0.8 magnitude units, primarily due to the initial P phase not containing the total seismic moment release. Long-period phases such as the W -phase and surface waves that better characterize total moment release can also be incorporated in the processing.
    Print ISSN: 0037-1106
    Electronic ISSN: 1943-3573
    Topics: Geosciences , Physics
    Published by Seismological Society of America (SSA)
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  • 10
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    High-Frequency Attenuation in the Lake Van Region, Eastern Turkey (2014)
    Seismological Society of America (SSA)
    Details
    Publication Date: 2014-06-12
    Description: We provide a complete description of the characteristics of excitation and attenuation of the ground motion in the Lake Van region (eastern Turkey) using a data set that includes three-component seismograms from the 23 October 2011 M w  7.1 Van earthquake, as well as its aftershocks. Regional attenuation and source scaling are parameterized to describe the observed ground motions as a function of distance, frequency, and magnitude. Peak ground velocities are measured in selected narrow frequency bands from 0.25 to 12.5 Hz; observed peaks are regressed to define a piecewise linear regional attenuation function, a set of excitation terms, and a set of site response terms. Results are modeled through random vibration theory (see Cartwright and Longuet-Higgins, 1956 ). In the log–log space, the regional crustal attenuation is modeled with a bilinear geometrical spreading characterized by a crossover distance at 40 km: fits our results at short distances ( r 〈40 km), whereas is better at larger distances (40〈 r 〈200 km). A frequency-dependent quality factor, Q ( f )=100( f / f ref ) 0.43 (in which f ref =1.0 Hz), is coupled to the geometrical spreading. Because of the inherent trade-off of the excitation/attenuation parameters ( and ), their specific values strongly depend on the choice made for the stress drop of the smaller earthquakes. After choosing a Brune stress drop Brune =4 MPa at M w =3.5, we were able to define (1) an effective high frequency, distance- and magnitude-independent roll-off spectral parameter, eff =0.03 s and (2) a size-dependent stress-drop parameter, which increases with moment magnitude, from Brune =4 MPa at M w  3.5 to Brune =20 MPa at M w  7.1. The set of parameters mentioned here may be used in order to predict the earthquake-induced ground motions expected from future earthquakes in the region surrounding Lake Van.
    Print ISSN: 0037-1106
    Electronic ISSN: 1943-3573
    Topics: Geosciences , Physics
    Published by Seismological Society of America (SSA)
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