[en] In recent years, seismic time series has been used to construct complex network models in order to describe the seismic complexity. The effect of the factor focal depth has been elided in some of these models. In this paper, we aim to construct a new complex network model for seismicity by considering depth factor from the earthquake catalog and investigate the statistical properties of the network. Since the networks have been proved to be scale-free and small-world properties, the new network models should be studied whether the properties have changed. The results show that the new network model by considering depth factor is still scale-free and small-world. However, it is found that its average degree is smaller than the original network. The clustering coefficient increases at the year including mainshocks. The assortativity coefficient, which demonstrates preferential attachment of nodes, is positive and shows consistent pattern when main shocks occur.

[en] Paleoseismology techniques have been applied across the CEUS (Central and Eastern United States) to augment seismic data and to improve seismic hazard analyses. Considering paleoseismic data along with historic data may increase the number of events and their maximum magnitudes (Mmax), which may decrease the recurrence time of seismic events included in hazard calculations. More importantly, paleoseismic studies extend the length of the earthquake record often by 1000s–10,000s of years and reduce uncertainties related to sources, magnitude, and recurrence times of earthquakes. The CEUS Seismic Source Characterization (Technical Report, [108]) uses a lot of paleoseismic data in building the source model for seismic hazard analyses. Most of these data are derived through study of paleoliquefaction features. Appendix E of the Technical Report compiles data from ten distinct regions in eastern North America where paleoliquefaction features have been used to improve knowledge of regional seismic history. These regions are shown. Paleoliquefaction data can significantly impact seismic hazard calculations by better defining earthquake sources, Mmax for those sources, and recurrence rates of large earthquakes

[en] In this study, five non-invasive swept sources, three non-invasive impulsive sources and one invasive impulsive source were compared. Previous shallow seismic source tests (Miller and others, 1986, 1992, 1994) have established that site characteristics should be considered in determining the optimal source. These studies evaluated a number of invasive sources along with a few non-invasive impulsive sources. Several sources (particularly the high frequency vibrators) that were included in the ORR test were not available or not practical during previous tests, cited above. This study differs from previous source comparisons in that it (1) includes many swept sources, (2) is designed for a greater target depth, (3) was conducted in a very different geologic environment, and (4) generated a larger and more diverse data set (including high fold CMP sections and walkaway vertical seismic profiles) for each source. The test site is centered around test injection well HF-2, between the southern end of Waste Area Grouping 5 (WAG 5) and the High Flux Isotope Reactor (HFIR)

[en] The majority of original seismograms recorded at the very beginning of instrumental seismology (the early 1900s) did not survive till present. However, a number of books, bulletins, and catalogs were published including the seismogram reproductions of some, particularly interesting earthquakes. In case these reproductions contain the time and amplitude scales, they can be successfully analyzed the same way as the original records. Information about the Atushi (Kashgar) earthquake, which occurred on August 22, 1902, is very limited. We could not find any original seismograms for this earthquake, but 12 seismograms from 6 seismic stations were printed as example records in different books. These data in combination with macroseismic observations and different bulletins information published for this earthquake were used to determine the source parameters of the earthquake. The earthquake epicenter was relocated at 39.87° N and 76.42° E with the hypocenter depth of about 18 km. We could further determine magnitudes m_B = 7.7 ± 0.3, M_S = 7.8 ± 0.4, M_W = 7.7 ± 0.3 and the focal mechanism of the earthquake with strike/dip/rake − 260°± 20/30°± 10/90°± 10. This study confirms that the earthquake likely had a smaller magnitude than previously reported (M8.3). The focal mechanism indicates dominant thrust faulting, which is in a good agreement with presumably responsible Tuotegongbaizi-Aerpaleike northward dipping thrust fault kinematic, described in previous studies.

[en] Romania has one of the highest seismic hazard levels in Europe. The seismic hazard is due to a combination of local crustal seismic sources, situated mainly in the western part of the country and the Vrancea intermediate-depth seismic source, which can be found at the bend of the Carpathian Mountains. Recent seismic hazard studies have shown that there are consistent differences between the slopes of the seismic hazard curves for sites situated in the fore-arc and back-arc of the Carpathian Mountains. Consequently, in this study we extend this finding to the evaluation of the probability of collapse of buildings and finally to the development of uniform risk-targeted maps. The main advantage of uniform risk approach is that the target probability of collapse will be uniform throughout the country. Finally, the results obtained are discussed in the light of a recent study with the same focus performed at European level using the hazard data from SHARE project. The analyses performed in this study have pointed out to a dominant influence of the quantile of peak ground acceleration used for anchoring the fragility function. This parameter basically alters the shape of the risk-targeted maps shifting the areas which have higher collapse probabilities from eastern Romania to western Romania, as its exceedance probability increases. Consequently, a uniform procedure for deriving risk-targeted maps appears as more than necessary.

[en] A reliable and homogenized earthquake catalogue is essential for seismic hazard assessment in any area. This article describes the compilation and processing of an updated earthquake catalogue for Pakistan. The earthquake catalogue compiled in this study for the region (quadrangle bounded by the geographical limits 40–83° N and 20–40° E) includes 36,563 earthquake events, which are reported as 4.0–8.3 moment magnitude (M_W) and span from 25 AD to 2016. Relationships are developed between the moment magnitude and body, and surface wave magnitude scales to unify the catalogue in terms of magnitude M_W. The catalogue includes earthquakes from Pakistan and neighbouring countries to minimize the effects of geopolitical boundaries in seismic hazard assessment studies. Earthquakes reported by local and international agencies as well as individual catalogues are included. The proposed catalogue is further used to obtain magnitude of completeness after removal of dependent events by using four different algorithms. Finally, seismicity parameters of the seismic sources are reported, and recommendations are made for seismic hazard assessment studies in Pakistan.

[en] Maximum intensity maps (MIM) may represent, as a first approach, the seismic risk of a certain region. In Portugal, the last MIM dates back to the eighties, suffering minor updates since then, and was based on the intensity distribution (isoseismals) of the major earthquakes affecting Portugal. Using GIS, we draw a more detailed map, not based on the isoseismal curves but based on the individual observations (intensity data points). A revision and compilation of all available macroseismic information was performed resulting on 5544 intensity data points (IDP). A MIM was produced using kriging interpolation in a GIS but inserting also the individual observations. The differences and similarities between this map and the previous one are discussed. To compare with the seismic zoning presented in the Portuguese seismic code, we performed, separately, a MIM considering only the earthquakes occurring on the NEAR seismic source zones and other MIM considering only the FAR seismic source zones. These maps were compared to the Portuguese seismic code zoning. The results obtained and discussed in this study present a high level of detail and could contribute for a better definition and estimation of the seismic hazard and risk in Portugal.

[en] The April 20, 2013 Lushan earthquake which occurred in Sichuan, China had only moderate thrust. However, the computed seismic moments (M₀) for the Lushan earthquake calculated by several institutions differ significantly from 0.4 × 10¹⁹ to 1.69 × 10¹⁹ Nm, up to four times difference. We evaluate ten computed M₀s by using normal mode observations from superconducting gravimeters in Mainland China. We compute synthetic normal modes on the basis of moment tensor solutions and fit them to the observed normal modes. Comparison of our results indicates that M₀ is the main cause for some large differences between observations and synthetics. We suggest that a moment magnitude of M_w6.6, corresponding to a M₀ of 0.97–1.08 × 10¹⁹ Nm, characterizes the size and strength of the seismic source of the Lushan earthquake.

[en] The Hanford Seismic Assessment Program (HSAP) provides an uninterrupted collection of high-quality raw and processed seismic data from the Hanford Seismic Network for the U.S. Department of Energy and its contractors. The Hanford Seismic Assessment Team locates and identifies sources of seismic activity and monitors changes in the historical pattern of seismic activity at the Hanford Site. The data are compiled, archived, and published for use by the Hanford Site for waste management, natural phenomena hazards assessments, and engineering design and construction. In addition, the seismic monitoring organization works with the Hanford Site Emergency Services Organization to provide assistance in the event of a significant earthquake on the Hanford Site. The Hanford Seismic Network and the Eastern Washington Regional Network consist of 44 individual sensor sites and 15 radio relay sites maintained by the Hanford Seismic Assessment Team. For the Hanford Seismic Network, seven local earthquakes were recorded during the second quarter of fiscal year 2008. The largest event recorded by the network during the second quarter (February 3, 2008 - magnitude 2.3 Mc) was located northeast of Richland in Franklin County at a depth of 22.5 km. With regard to the depth distribution, two earthquakes occurred at shallow depths (less than 4 km, most likely in the Columbia River basalts), three earthquakes at intermediate depths (between 4 and 9 km, most likely in the pre-basalt sediments), and two earthquakes were located at depths greater than 9 km, within the crystalline basement. Geographically, five earthquakes occurred in swarm areas and two earthquakes were classified as random events

[en] By means of ten-month observation data, recorded by IS31-Aktyubinsk infrasound station, correlation between the recorded infrasound signals and flambeau lights of oil-well gas at Zhanazhol pit, located at 235 km to the south from the station, was found. The obtained result is used to determine infrasound events for bulletin. (author)