70 research outputs found
The 6 May 1976 Friuli earthquake: re-evaluating and consolidating
The aim of this paper is to propose the creation, in terms of European Macroseismic
Scale (EMS-98), of the entire macroseismic fi eld of the 6 May 1976 Friuli earthquake.
Only forty odd years have passed, and nothwithsatnding that there is a huge quantity
of existing data, it was still disturbing to fi nd that much of the original data are missing
and probably lost forever Efforts have therefore been made to fi nd additional and
still unknown primary data. For the majority of the collected national data sets, a reevaluation
was then possible. This study presents the comprehensive macroseismic
data set for 14 European countries. It is, to our knowledge, one of the largest European
data sets, consisting of 3423 intensity data points (IDPs). The earthquake was felt from
Rome to the Baltic Sea, and from Belgium to Warsaw. The maximum intensity 10
EMS-98 was reached in eight localities in Friuli (Italy). Compared to previous studies,
the Imax values have changed from country to country, in some cases being lowered due
to methodological differences, but in the case of three among the most hit countries,
Imax is now higher than in the previous studies, mainly due to the new data.Published417-4444T. SismicitĂ dell'ItaliaJCR Journa
The MPIfR-MeerKAT Galactic Plane Survey: II. The eccentric double neutron star system PSR J1208a-5936 and a neutron star merger rate update
The MPIfR-MeerKAT Galactic Plane survey at L-band (MMGPS-L) is the most sensitive pulsar survey in the Southern Hemisphere, providing 78 discoveries in an area of 900 sq. deg. Here, we present a follow-up study of one of these new discoveries, PSR J1208a-5936, a 28.71-ms recycled pulsar in a double neutron star system with an orbital period of Pb=0.632 days and an eccentricity of e=0.348, merging within the Hubble time. Through timing of almost one year of observations, we detected the relativistic advance of periastron ( à = 0.918(1) deg yra-1), resulting in a total system mass of Mt=2.586(5) M·. We also achieved low-significance constraints on the amplitude of the Einstein delay and Shapiro delay, in turn yielding constraints on the pulsar mass (Mp = 1.26a-0.25+0.13 M·), the companion mass (Mc = 1.32a-0.13+0.25 M·), and the inclination angle (i=57 ± 12). This system is highly eccentric compared to other Galactic field double neutron stars with similar periods, possibly hinting at a larger-than-usual supernova kick during the formation of the second-born neutron star. The binary will merge within 7.2(2) Gyr due to the emission of gravitational waves, making it a progenitor of the neutron star merger events seen by ground-based gravitational wave observatories. With the improved sensitivity of the MMGPS-L, we updated the Milky Way neutron star merger rate to be RMWnew = 25a-9+19 Myra-1 within 90% credible intervals, which is lower than previous studies based on known Galactic binaries owing to the lack of further detections despite the highly sensitive nature of the survey. This implies a local cosmic neutron star merger rate of Rlocalnew = 293a-103+222 Gpca-3 yra-1, which is consistent with LIGO and Virgo O3 observations. With this, we also predict the observation of 10a-4+8 neutron star merger events during the LIGO-Virgo-KAGRA O4 run. We predict the uncertainties on the component masses and the inclination angle will be reduced to 5- 10a-3 M· and 0.4 after two decades of timing, and that in at least a decade from now the detection of b and the sky proper motion will serve to make an independent constraint of the distance to the system
The MPIfR-MeerKAT Galactic Plane Survey II. The eccentric double neutron star system PSR J1208-5936 and a neutron star merger rate update
The MMGPS-L is the most sensitive pulsar survey in the Southern Hemisphere.
We present a follow-up study of one of these new discoveries, PSR J1208-5936, a
28.71-ms recycled pulsar in a double neutron star system with an orbital period
of Pb=0.632 days and an eccentricity of e=0.348. Through timing of almost one
year of observations, we detected the relativistic advance of periastron
(0.918(1) deg/yr), resulting in a total system mass of Mt=2.586(5) Mo. We also
achieved low-significance constraints on the amplitude of the Einstein delay
and Shapiro delay, in turn yielding constraints on the pulsar mass
(Mp=1.26(+0.13/-0.25) Mo), the companion mass (Mc=1.32(+0.25/-0.13) Mo, and the
inclination angle (i=57(2) degrees). This system is highly eccentric compared
to other Galactic field double neutron stars with similar periods, possibly
hinting at a larger-than-usual supernova kick during the formation of the
second-born neutron star. The binary will merge within 7.2(2) Gyr due to the
emission of gravitational waves. With the improved sensitivity of the MMGPS-L,
we updated the Milky Way neutron star merger rate to be 25(+19/-9) Myr
within 90% credible intervals, which is lower than previous studies based on
known Galactic binaries owing to the lack of further detections despite the
highly sensitive nature of the survey. This implies a local cosmic neutron star
merger rate of 293(+222/-103} Gpc/yr, consistent with LIGO and Virgo O3
observations. With this, we predict the observation of 10(+8/-4) neutron star
merger events during the LIGO-Virgo-KAGRA O4 run. We predict the uncertainties
on the component masses and the inclination angle will be reduced to
5x10 Mo and 0.4 degrees after two decades of timing, and that in at
least a decade from now the detection of the shift in Pb and the sky proper
motion will serve to make an independent constraint of the distance to the
system
Comparing recent PTA results on the nanohertz stochastic gravitational wave background
The Australian, Chinese, European, Indian, and North American pulsar timing
array (PTA) collaborations recently reported, at varying levels, evidence for
the presence of a nanohertz gravitational wave background (GWB). Given that
each PTA made different choices in modeling their data, we perform a comparison
of the GWB and individual pulsar noise parameters across the results reported
from the PTAs that constitute the International Pulsar Timing Array (IPTA). We
show that despite making different modeling choices, there is no significant
difference in the GWB parameters that are measured by the different PTAs,
agreeing within . The pulsar noise parameters are also consistent
between different PTAs for the majority of the pulsars included in these
analyses. We bridge the differences in modeling choices by adopting a
standardized noise model for all pulsars and PTAs, finding that under this
model there is a reduction in the tension in the pulsar noise parameters. As
part of this reanalysis, we "extended" each PTA's data set by adding extra
pulsars that were not timed by that PTA. Under these extensions, we find better
constraints on the GWB amplitude and a higher signal-to-noise ratio for the
Hellings and Downs correlations. These extensions serve as a prelude to the
benefits offered by a full combination of data across all pulsars in the IPTA,
i.e., the IPTA's Data Release 3, which will involve not just adding in
additional pulsars, but also including data from all three PTAs where any given
pulsar is timed by more than as single PTA.Comment: 21 pages, 9 figures, submitted to Ap
Comparing Recent Pulsar Timing Array Results on the Nanohertz Stochastic Gravitational-wave Background
The Australian, Chinese, European, Indian, and North American pulsar timing array (PTA) collaborations recently reported, at varying levels, evidence for the presence of a nanohertz gravitational-wave background (GWB). Given that each PTA made different choices in modeling their data, we perform a comparison of the GWB and individual pulsar noise parameters across the results reported from the PTAs that constitute the International Pulsar Timing Array (IPTA). We show that despite making different modeling choices, there is no significant difference in the GWB parameters that are measured by the different PTAs, agreeing within 1Ï. The pulsar noise parameters are also consistent between different PTAs for the majority of the pulsars included in these analyses. We bridge the differences in modeling choices by adopting a standardized noise model for all pulsars and PTAs, finding that under this model there is a reduction in the tension in the pulsar noise parameters. As part of this reanalysis, we "extended" each PTA's data set by adding extra pulsars that were not timed by that PTA. Under these extensions, we find better constraints on the GWB amplitude and a higher signal-to-noise ratio for the HellingsâDowns correlations. These extensions serve as a prelude to the benefits offered by a full combination of data across all pulsars in the IPTA, i.e., the IPTA's Data Release 3, which will involve not just adding in additional pulsars but also including data from all three PTAs where any given pulsar is timed by more than a single PTA
Site-specific response spectra from the combination of microzonation with probabilistic seismic hazard assessment - An example for the Cologne (Germany) area
Seismic noise was measured at some 20 sites in the Cologne area (Germany) aligned nearly perpendicular to a graben structure. The H/V spectral noise ratio for each site was used to derive realistic S-wave velocity profiles down to the bedrock by means of a genetic algorithm inversion. Numerical simulations were performed for different combinations of source and propagation path parameters: focal depth, epicentral distance, attenuation and fault mechanism. Synthetic seismograms were produced and converted to Fourier and response spectra. Finally, the site-specific values from response spectral ratios, with their uncertainties, were used to modify attenuation functions entering the logic-tree algorithm of the probabilistic seismic hazard assessment (PSHA). The site-specific response spectra show the significance of taking into account the local S-wave velocity structure in PSHA. (c) 2006 Elsevier Ltd. All rights reserved
Seismic hazard assessment for Central, North and Northwest Europe: GSHAP Region 3
The activities of the Regional Centre 3 of the Global Seismic Hazard Assessment Program (GSHAP) covering Europe north of 46°N and west of 32°E are summarized starting with the establishment of the GSHAP Centre at the GFZ Potsdam in 1993 and leading finally in the calculation and creation of the GSHAP seismic hazard map in terms of horizontal Peak Ground Acceleration (PGA). Moreover, the activities of separate working groups which contribute with their results for certain parts of the study area to the final product of the Regional Centre are described. Details are given on the development of the homogeneous seismicity working file, the delineation of seismic source zones, the data preprocessing as well as on the chosen PGA-attenuation relations
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