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  • Open access
  • 109 Reads
Statistical analysis of the Taiwanese shallow seismicity by using fractal and spectral methods

The whole and aftershock-depleted shallow (depth ≤30 km) seismicity of Taiwan from 1990 to 2017 was investigated by using fractal and spectral methods. The global and local coefficient of variation and the Allan Factor showed that the time distribution of both the whole and aftershock-depleted seismic catalogues are characterized by time-clustering structures. In particular, at small timescales the seismicity of the whole and aftershock-depleted catalogues can be represented as a Poisson process. Persistent time fluctuations have been identified in the interevent time series, while weak persistence or randomness in the magnitude series. By applying the singular spectrum analysis to the daily number of events of the aftershock-depleted catalogue, quasi-monthly and bi-weekly periodicities were revealed. Furthermore, the correlation between the Taiwanese seismic activity and Earth’s tides was suggested by the appearance of quasi-annual and quasi-semestral periodicities.

  • Open access
  • 117 Reads
Complex networks analysis along the Chilean subduction zone: degree distribution characterization

A time-based complex network analysis on the seismic activity along the coast of Chile was made. The study was made by using a moving window along the chilean subduction zone. The coast of Chile was divided on windows of 300 km in Latitude, from Arica city in the north up to Temuco city, in the south. The window was moved in 100 km from north to south. We built a time-based earthquake complex network on each window and we studied a directed complex network along the Chilean coast. Assuming a self-similar data network for the directed network we found the value of the power law characteristic exponent for the connectivity probability distribution. The exponents and values were evaluated for the data set with magnitude greater than Mw 3.0. We compare the results with previous works that measured the coupling along the Chilean coast.

  • Open access
  • 130 Reads
Seismic b-value study in southern slope of Greater Caucasus (Azerbaijan)

In this study, there was an attempt to estimate seismic hazard in terms of b-value distribution over the southern slope of Greater Caucasus (Azerbaijan). The southern slope of Caucasus (Azerbaijan) is influenced by the tectonic activity driven by Arabian and Eurasian plate tectonics. The differences between seismotectonic characteristics are considered for the large tectonic zones within this southern slope (Balaken-Zaqatala, Sheki-Oguz-Gabala, Ismailli-Shamakhi). The b-value is one of the important components in the Gutenberg-Richter empirical relation. This relation represents the frequency of occurrence of seismic events as a function of their magnitude. The a-value and the b-value in this relation are constants and they characterize the seismic features. The a-value describes the seismic activity in terms of spatial and temporal occurrences within the certain period, while the b-value measures the relation of the strong to the weak earthquakes. The b-value indicates the dynamics of the tectonic regime of the area. This constant demonstrates the distribution of the low or the high stresses. The data for this study has been extracted from the Azerbaijan seismological center (RCSS). Then different relations have been developed for each separate zone. Some studies revealed the spatial and temporal variations of the b-value before large earthquakes during the last decades. The b-value distribution result shows that the decrease is observed in the western part of the region (Zagatala, Sheki), in the Shamakhi area and on some areas of the northern part which is an indication of higher stress in those areas.

  • Open access
  • 58 Reads
Fractal and multifractal features of seismicity in the central zone of Chile: comparing intraplate and interplate datasets

A fractal and multifractal study on a sample of superficial interplate and intraplate earthquakes in the central zone of Chile is made. Epicenter and hypocenter data are considered. We find that the fractal dimension and the multifractal spectrum exhibit dependence on location, which suggests that these measures of
complexity are able to distinguish interplate and intraplate seismicity.

  • Open access
  • 189 Reads
Some common properties between actual seismicity, the spring-block model and experiments with sandpapers

We present a study about some common features between actual seismicity, a self-organized critical model (the spring-block model) and frictional experiments made with sandpapers. We found a correlation between the b-value of the Gutenberg-Richter law (log N=a+bM), relationship which relates the seismic frequency with the magnitudes of the seismic events in a certain seismic region, and the gamma value which plays the role of an elastic ratio in the spring-block model. After the analysis made, we could establish that there is a parallel behavior between gamma, age and weathering, since gamma value plays in the spring-block model the role that age plays in the subduction plates in actual seismicity and weathering in experiments with sandpapers. We could established also a correlation between gamma value and the connectivity of the synthetic series made with the spring-block model. A synthetic reproduction of the Ruff-Kanamori diagram was also achieved.

  • Open access
  • 221 Reads
Land Subsidence Monitoring in Jagadhri city using Sentinel 1 DInSAR Processing

DInSAR is a renowned method for estimating land subsidence based on the principles of Interferometric Synthetic Aperture Radar using different series of the temporal dataset. The present study has been performed using GMTSAR software with Sentinel 1 SAR data of C band for the duration of 2017-2019 (January to April) and focused particularly over the area of Jagadhri city which is situated 100Km away from Chandigarh, which has been identified under the potential threat of land subsidence. The DInSAR method has been applied in this study that came up with an outcome of 3 interferograms and yearly displacement that broadcast an update on the diagnosis of subsidence activity in the area. Total 6 SLC dataset was selectively chosen with a minimum temporal and spatial baseline so that the problem of decorrelation would be minimal. Goldstein filtering has been applied to the debursted interferograms which reduced the noise and in turn improved the quality of output. The city is located on the western bank of river Yamuna and about 55Km on the east of Ambala Due to the presence of unconsolidated sediments in the aquifer system and overexploitation of groundwater to meet the domestic needs has led to surface deformation in and around the city area. The outcome of this study identifies the area of depression quite distinctly while the accuracy has been assessed by ground survey. The rate of subsidence estimated approximately 4.9 cm/year which can prove to be disastrous over the course of time.