Reliability of Source Parameters for Small Events in Central Italy: Insights from Spectral Decomposition Analysis Applied to Both Synthetic and Real Data

2020 ◽  
Vol 110 (6) ◽  
pp. 3139-3157
Author(s):  
Dino Bindi ◽  
Daniele Spallarossa ◽  
Matteo Picozzi ◽  
Paola Morasca
Keyword(s):  
Spectral Decomposition ◽  
Source Parameters ◽  
Central Italy ◽  
Data Availability ◽  
Moment Magnitude ◽  
Corner Frequency ◽  
Data Set ◽  
Near Surface ◽  
Source Scaling ◽  
Source Spectra

ABSTRACT We apply a spectral decomposition approach to isolate the source spectra from propagation and site effects and, in turn, to estimate the source parameters of small-to-moderate earthquakes that occurred in central Italy. The data set is composed of about 400,000 waveforms relevant to 4111 earthquakes in the moment magnitude range 1.5–6.5, recorded by a high-density network of stations installed in the study area. We first investigate the reliability of the source parameters for small magnitudes through numerical simulations. We generate synthetic spectra for different source scaling models and near-surface attenuation effects, considering the source–station geometry and the data availability of the central Italy data set. Our analysis with synthetics shows that the spectral decomposition is effective in isolating the source contributions from other factors. Moreover, the analysis of the residual distributions suggests that moment magnitude 1.8 is the lower bound for the retrieval of reliable Brune’s source parameters, although we observe an increase of residual’s variability below magnitude 3, and the estimated source parameters could be biased below magnitude 2.3. Remarkably, the assessment of the stress drop Δσ for small events is strongly hampered by site-specific attenuation near the surface. In view of the results with synthetics, we analyze the source parameters of earthquakes recorded in central Italy. The corner frequency versus seismic moment relationship describes a source scaling in which Δσ increases with increasing moment magnitude Mw, the mean Δσ varying from 0.1 MPa for Mw<2 to 7.9 MPa for Mw>5. In particular, Δσ increases mainly for Mw in the ranges 2.5–3 and 4.5–5.2. The corner frequencies estimated from the apparent source spectra do not show any dependence on hypocentral distance and magnitude, confirming that uncorrected anelastic attenuation effects do not significantly bias the results.

scholarly journals Fast and Robust Earthquake Source Spectra and Moment Magnitudes from Envelope Inversion

2021 ◽  
Author(s):  
Tom Eulenfeld ◽  
Torsten Dahm ◽  
Sebastian Heimann ◽  
Ulrich Wegler
Keyword(s):  
Source Parameters ◽  
Earthquake Swarm ◽  
Earthquake Source ◽  
Body Waves ◽  
Corner Frequency ◽  
Data Set ◽  
Displacement Spectra ◽  
Short Period ◽  
Source Spectra ◽  
Good Agreement

ABSTRACT With the present study, we introduce a fast and robust method to calculate the source displacement spectra of small earthquakes on a local to regional scale. The work is based on the publicly available Qopen method of full envelope inversion, which is further tuned for the given purpose. Important source parameters—seismic moment, moment magnitude, corner frequency, and high-frequency fall off—are determined from the source spectra by fitting a simple earthquake source model. The method is demonstrated by means of a data set comprising the 2018 West Bohemia earthquake swarm. We report moment magnitudes, corner frequencies, and centroid moment tensors inverted from short-period body waves with the Grond package for all earthquakes with a local magnitude larger than 1.8. Moment magnitudes calculated by envelope inversion show a very good agreement to moment magnitudes resulting from the probabilisitc moment tensor inversion. Furthermore, source displacement spectra from envelope inversion show a good agreement with spectra obtained by multiple taper analysis of the direct onsets of body waves but are not affected by the large scatter of the second. The seismic moments obtained with the envelope inversion scale with corner frequencies according to M0∝fc−4.7. Earthquakes of the present data set result in a smaller stress drop for smaller magnitudes. Self-similarity of earthquake rupture is not observed. In addition, we report frequency-dependent site amplification at the used stations.

The characteristic of source spectra and stress drop of earthquakes in the Bucaramanga nest

2020 ◽  
Author(s):  
Wenzheng Gong ◽  
Xiaofei Chen
Keyword(s):  
Focal Mechanism ◽  
Stress Drop ◽  
Source Parameters ◽  
Time Function ◽  
Corner Frequency ◽  
Ratio Method ◽  
Source Time Function ◽  
Spectra Analysis ◽  
Source Spectra ◽  
Very High

<p>Spectra analysis is helpful to understand earthquake rupture processes and estimate source parameters like stress drop. Obtaining real source spectra and source time function isn’t easy, because the station recordings contain path effect and we usually can’t get precise path information. Empirical Green’s function (EGF) method is a popular way to cancel out the path effect, main two of which are the stacking spectra method (Prieto et al, 2006) and the spectral ratio method (Viegas et al, 2010; Imanishi et al, 2006). In our study, we apply the latter with multitaper spectral analysis method (Prieto et al, 2009) to calculate relative source spectra and relative source time function. Target event and EGFs must have similar focal mechanism and be collocated, so we combine correlation coefficient of wave at all stations and focal mechanism similarity to select proper EGFs.</p><p>The Bucaramanga nest has very high seismicity, so it’s suitable to calculate source spectra by using EGF method. We calculate the source spectra and source time function of about 1540 earthquakes (3-5.7ml, 135-160km depth) at Bucaramanga nest in Colombia. Simultaneously we also estimate corner frequency by fitting spectral source model (Brune, 1970; Boatwright, 1980) and stress drop using simple model (Eshelby, 1957) of earthquakes with multiple station recordings or EGFs. We obtain about 30000 events data with 12 stations from National Seismological Network of Colombia (RSNC).</p><p>The result show that the source spectra of most earthquakes fitted well by omega-square model are smooth, and the source spectra of some have obvious ‘holes’ near corner frequency, and the source time function of a few earthquakes appear two separate peeks. The first kind of earthquakes are style of self-arresting ruptures (Xu et al. 2015), which can be autonomously arrested by itself without any outside interference. Abercrombie (2014) and Wen et al. (2018) both researched the second kind of earthquakes and Wen think that this kind of earthquakes are style of the runaway ruptures including subshear and supershear ruptures. The last kind of earthquakes maybe be caused by simultaneous slip on two close rupture zone. Stress drop appear to slightly increase with depth and are very high (assuming rupture velocity/s wave velocity is 0.9). We also investigate the high-frequency falloff n, usually 2, of Brune model and Boatwright model by fitting all spectra, and find that the best value of n for Boatwright model is 2 and for Brune model is 3.5.</p>

scholarly journals Using Seismic Attributes in seismotectonic research: an application to the Norcia's Mw = 6.5 earthquake (30th October 2016) in Central Italy

2019 ◽  
Author(s):  
Maurizio Ercoli ◽  
Emanuele Forte ◽  
Massimiliano Porreca ◽  
Ramon Carbonell ◽  
Cristina Pauselli ◽  
...  
Keyword(s):  
Seismic Reflection ◽  
Central Italy ◽  
Seismic Attributes ◽  
Seismic Attribute ◽  
Data Set ◽  
Epicentral Zone ◽  
Seismic Reflection Data ◽  
Near Surface ◽  
Reflection Data ◽  
Attribute Analysis

Abstract. In seismotectonic studies, seismic reflection data are a powerful tool to unravel the complex deep architecture of active faults. Such tectonic structures are usually mapped at surface through traditional geological surveying whilst seismic reflection data may help to trace their continuation from the near-surface down to hypocentral depth. In this study, we propose the application of the seismic attributes technique, commonly used in seismic reflection exploration by oil industry, to seismotectonic research for the first time. The study area is a geologically complex region of Central Italy, recently struck by a long-lasting seismic sequence including a Mw 6.5 main-shock. A seismic reflection data-set consisting of three vintage seismic profiles, currently the only available across the epicentral zone, constitutes a singular opportunity to attempt a seismic attribute analysis. This analysis resulted in peculiar seismic signatures which generally correlate with the exposed surface geologic features, and also confirming the presence of other debated structures. These results are critical, because provide information also on the relatively deep structural setting, mapping a prominent, high amplitude regional reflector that marks the top basement, interpreted as important rheological boundary. Complex patterns of high-angle discontinuities crossing the reflectors have been also identified. These dipping fabrics are interpreted as the expression of fault zones, belonging to the active normal fault systems responsible for the seismicity of the region. This work demonstrates that seismic attribute analysis, even if used on low-quality vintage 2D data, may contribute to improve the subsurface geological interpretation of areas characterized by high seismic potential.

Source parameters and scaling laws of the 1978 Swabian Jura (southwest Germany) aftershocks

1983 ◽  
Vol 73 (5) ◽  
pp. 1321-1343
Author(s):  
Frank Scherbaum ◽  
Dieter Stoll
Keyword(s):  
Scaling Laws ◽  
Source Parameters ◽  
Source Model ◽  
Local Network ◽  
Corner Frequency ◽  
Strong Increase ◽  
Crack Model ◽  
Data Set ◽  
Stress Drops ◽  
Southwest Germany

Abstract The 3 September 1978, Swabian Jura (southwest Germany) earthquake (MWA = 5.7) was followed by a large number of aftershocks which have been recorded with a local network of five portable seismic stations. The seismic moments, fault radii, and the static stress drops have been determined from the SH displacement spectra using the Brune (1970) source model. The data set is consistent with the Gutenberg-Richter energy-magnitude relation. Below a Wood-Anderson magnitude of about 4, the corner frequencies increase only slowly with decreasing magnitudes. No corner frequency higher than 15 Hz has been observed in the magnitude range down to 0.8. Correspondingly, the high-frequency decay slopes show a strong increase when the corner frequencies are approaching the maximum frequency. This prevents the use of slope data for Q determinations. In terms of the Madariaga (1977) crack model, the data show a strong influence of source complexities on the smaller events.

SEISMOLOGICAL AND ENGINEERING PARAMETERS OF 24 and 26 SEPTEMBER, 2019 MARMARA SEA EARTHQUAKES

2020 ◽  
Author(s):  
Eser Çakti ◽  
Fatma Sevil Malcioğlu ◽  
Hakan Süleyman
Keyword(s):  
Earthquake Engineering ◽  
Prediction Models ◽  
Source Parameters ◽  
Strong Motion ◽  
P Wave ◽  
Corner Frequency ◽  
Marmara Sea ◽  
S Wave ◽  
Data Set ◽  
The North

<p>On 24<sup>th</sup> and 26<sup>th</sup>  September 2019, two earthquakes of M<sub>w</sub>=4.5 and M<sub>w</sub>=5.6 respectively took place in the Marmara Sea. They were associated with the Central Marmara segment of the North Anatolian Fault Zone, which is pinpointed by several investigators as the most likely segment to rupture in the near future giving way to an earthquake larger than M7.0. Both events were felt widely in the region. The M<sub>w</sub>=5.6 event, in particular, led to a number of building damages in Istanbul, which were larger than expected in number and severity. There are several strong motion networks in operation in and around Istanbul. We have compiled a data set of recordings obtained at the stations of the Istanbul Earthquake Rapid Response and Early Warning operated by the Department of Earthquake Engineering of Bogazici University and of the National Strong Motion Network operated by AFAD. It consists of 148 three component recordings, in total.  444 records in the data set, after correction, were analyzed to estimate the source parameters of these events, such as corner frequency, source duration, radius and rupture area, average source dislocation and stress drop. Duration characteristics of two earthquakes were analyzed first by considering P-wave and S-wave onsets and then, focusing on S-wave and significant durations. PGAs, PGVs and SAs were calculated and compared with three commonly used ground motion prediction models (i.e  Boore et al., 2014; Akkar et al., 2014 and Kale et al., 2015). Finally frequency-dependent Q models were estimated using the data set and their validity was dicussed by comparing with previously developed models.</p>

scholarly journals Thermally driven circulation in a region of complex topography: comparison of wind-profiling radar measurements and MM5 numerical predictions

2006 ◽  
Vol 24 (6) ◽  
pp. 1537-1549 ◽  
Author(s):  
L. Bianco ◽  
B. Tomassetti ◽  
E. Coppola ◽  
A. Fracassi ◽  
M. Verdecchia ◽  
...  
Keyword(s):  
Land Surface ◽  
Central Italy ◽  
Surface Wind ◽  
Lower Atmosphere ◽  
Complex Topography ◽  
Model Errors ◽  
Data Set ◽  
Near Surface ◽  
Numerical Predictions ◽  
Thermally Driven

Abstract. The diurnal variation of regional wind patterns in the complex terrain of Central Italy was investigated for summer fair-weather conditions and winter time periods using a radar wind profiler. The profiler is located on a site where interaction between the complex topography and land-surface produces a variety of thermally and dynamically driven wind systems. The observational data set, collected for a period of one year, was used first to describe the diurnal evolution of thermal driven winds, second to validate the Mesoscale Model 5 (MM5) that is a three-dimensional numerical model. This type of analysis was focused on the near-surface wind observation, since thermally driven winds occur in the lower atmosphere. According to the valley wind theory expectations, the site – located on the left sidewall of the valley (looking up valley) – experiences a clockwise turning with time. Same characteristics in the behavior were established in both the experimental and numerical results. Because the thermally driven flows can have some depth and may be influenced mainly by model errors, as a third step the analysis focuses on a subset of cases to explore four different MM5 Planetary Boundary Layer (PBL) parameterizations. The reason is to test how the results are sensitive to the selected PBL parameterization, and to identify the better parameterization if it is possible. For this purpose we analysed the MM5 output for the whole PBL levels. The chosen PBL parameterizations are: 1) Gayno-Seaman; 2) Medium-Range Forecast; 3) Mellor-Yamada scheme as used in the ETA model; and 4) Blackadar.

scholarly journals A SOURCE PARAMETERS STUDY OF THE AFTERSHOCK SEQUENCE OF THE KOZANI- GREVENA 1995 EARTHQUAKE BASED ON ACCELERATION RECORDS

2004 ◽  
Vol 36 (3) ◽  
pp. 1457 ◽  
Author(s):  
A. A. Panou ◽  
C. B. Papazachos ◽  
Ch. Papaioannou ◽  
P. M. Hatzidimitriou
Keyword(s):  
Source Parameters ◽  
Strong Motion ◽  
Aftershock Sequence ◽  
Propagation Path ◽  
Data Set ◽  
Near Surface ◽  
Anelastic Attenuation ◽  
Geological Formation ◽  
Good Agreement

Strong motion recordings of the May 13, 1995 Mw=6.6, earthquake sequence that occurred in the Kozani-Grevena region (Western Macedonia, Greece) have been analyzed for the determination of their source parameters. The data set for this study comes from a temporarily deployed accelerograph network and the source parameters using the shear-wave displacement spectra have been estimated. For this estimation the spectral records have been corrected for the site effects and for the propagation path (geometrical spreading and anelastic attenuation). The magnitude of each event was also re-calculated by estimating appropriate station corrections. The derived relationships arelogMo =(1.43 ±0.09) M, + (16.92 ± 0.29), 2.0 < ML< 5.0 (1)logfc = (-0.56± 0.08) · ML + (2.52 + 0.29), 2.0 < ML< 5.0 (2)logM0 = (-2.20 + 0.08) · log fc + (23.16 ± 0.84), 0.6 < fc < 10.0 (3)The near-surface attenuation parameter κ0 has also been determined for the strong motion stations sites. These values of κ0 are in good agreement with those of Margaris and Boore (1998) for the geological formation on which each station was positioned. The obtained source parameters are in good agreement with those from previous studies for the Aegean region.

scholarly journals ANALISIS PARAMETER SUMBER SPEKTRAL GEMPABUMI VTA (VULKANO TEKTONIK-A) TERHADAP AKTIVITAS VULKANIK GUNUNG SINABUNG

2019 ◽  
Vol 5 (1) ◽  
pp. 18-23
Author(s):  
Tri Kusmita ◽  
Kirbani Brotopuspito ◽  
Hetty Triastuty
Keyword(s):  
Stress Drop ◽  
Seismic Moment ◽  
Source Parameters ◽  
Radiation Energy ◽  
Angular Frequency ◽  
Moment Magnitude ◽  
Corner Frequency ◽  
Volcanic Earthquake ◽  
Seismic Volumes ◽  
The Relationship

The source parameters describe the different physical properties of seismic volumes under the volcanoes. Source parameters that can be used to distinguish seismic events that are generated by different types of volcanoes activities. Temporary changes of the spectral source parameters provided a description of the main events during the eruption process.  Source parameters are calculated by correlating the relationship between source frequency at spectral displacement (corner frequency) and source parameters based on spectral sources of the Brune model (1970). The angular frequency obtained by applying the FFT algorithm to the VTA spectral displacement. The source parameters analyzed from this VTA earthquake are the spectral slope, seismic moment, stress drop, length of rupture, moment magnitude and radiation energy. Based on the obtained corner frequency (12 Hz-13 Hz), seismic moment, moment magnitude and energy radiation respectively were at 0.2 -1.9 x 1012 Nm, 0.7 - 2 Mw, and 0.1 - 9.5 x 1015 erg. The length of rupture were from 144.2 to 243.1 m, the spectra slope has 2.1 - 7.8 dB/cm, and stress drop are 0.1 - 7,6 bar. From the results of this study, it can be concluded that the changes of spectra characteristic and fluctuate of source patrameters value of VTA earthquakes was asosiated with the different  volcanic activity of Sinabung. Keywords: spectral, VTA, source parameter, volcanic earthquake

Analysis of Source Parameters relationships for clusters of similar events recorded in Central Apennines

2020 ◽  
Author(s):  
Daniele Spallarossa ◽  
Paola Morasca ◽  
Dino Bindi ◽  
Matteo Picozzi ◽  
Kevin Mayeda
Keyword(s):  
Pulse Duration ◽  
Cross Correlation ◽  
Source Parameters ◽  
Quality Data ◽  
Corner Frequency ◽  
Central Apennines ◽  
Data Set ◽  
Small Magnitude ◽  
Decomposition Approach ◽  
Magnitude Range

&lt;p&gt;&lt;span&gt;&lt;span&gt;Aim of this study is to investigate the relationship between moment magnitude (Mw) and source duration (i.e. corner frequency) for moderate to small magnitude earthquakes recorded in Central Apennines, Italy, including the 2016-2017 Amatrice-Norcia-Visso&amp;#160;sequence. &lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;A data-set of ~ 6000&amp;#160;events in the magnitude range ~1 and&amp;#160; 6.5 was used to retrieve a reference data set of source parameters by applying spectral decomposition approach (Generalized Inversion Techniques). &lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;The large population of analyzed earthquakes allowed us to investigate the scaling of the source parameters with the earthquake size, their variability with hypocentral depth and to characterize the scaling between local and moment magnitudes in the magnitude range from 1 to 6.5 &lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;(&lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;Deichmann &lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;2017). &lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;Analyzing the same data-set and taking advantage of the available high quality data for small events recorded in &lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;the&lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt; area, we focus on the scaling properties of clustered events in the&amp;#160;magnitude range between ~1 and&amp;#160; 3.5. By applying different methodologies, relying on cross-correlation analysis, we detect a preliminary set of clusters. &lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;Then, events within 2 km from the geographic location of each cluster were extracted from a very large (more than 500000 events) high-resolution earthquake parametric catalog. New cross-correlation analyses were carried out on stations within 50 km from the centroid of each previously identified clusters to pad each ones with low magnitude events (below 2). &lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;This multi-steps procedure allowed us to identified 2933 events belonging to 45 clusters. &lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;For an in-deep analysis of source properties, we focus on three clusters selected on the basis of the number of events and different hypocentral depth distributions. For each cluster, the P-waves pulse duration (equivalent to &lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;corner&lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt; frequency) of the events were compared each other on different stations. Results clearly show that below Ml &lt;/span&gt;&lt;/span&gt; &lt;span&gt;&lt;span&gt;~ 2 the pulses duration remains nearly constant also for stations with low kappa values, showing a saturation effects. &lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;For a comparison with the GIT and cross-correlation results we also evaluate source parameters using a method based on coda-envelope amplitude measurements (Mayeda et al. 2003) applying site and path parameters previously calibrated for Central Apennines by Morasca et al. 2019. &lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;This comparison from independent and completely different methodologies applied on the same clusters well agrees with the saturation observed in pulse duration&lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;, &lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;strengthen the results and allowed us to define, for the given network geometry and earthquake distribution, the magnitude threshold below which we believe it is not possible to estimate source parameters. Moreover, our analysis of two clusters co-located on map but with different depth highlights a variation in stress drop with depth;&lt;/span&gt;&lt;/span&gt;&lt;/p&gt;

Financial distress determinants among SMEs: empirical evidence from Sweden

2020 ◽  
Vol 47 (3) ◽  
pp. 547-560 ◽  
Author(s):  
Darush Yazdanfar ◽  
Peter Öhman
Keyword(s):  
Financial Crisis ◽  
Financial Distress ◽  
Large Scale ◽  
Global Financial Crisis ◽  
Binary Logistic Regression ◽  
Data Availability ◽  
Cross Sectional ◽  
Data Set ◽  
Content Type ◽  
The Global Financial Crisis

PurposeThe purpose of this study is to empirically investigate determinants of financial distress among small and medium-sized enterprises (SMEs) during the global financial crisis and post-crisis periods.Design/methodology/approachSeveral statistical methods, including multiple binary logistic regression, were used to analyse a longitudinal cross-sectional panel data set of 3,865 Swedish SMEs operating in five industries over the 2008–2015 period.FindingsThe results suggest that financial distress is influenced by macroeconomic conditions (i.e. the global financial crisis) and, in particular, by various firm-specific characteristics (i.e. performance, financial leverage and financial distress in previous year). However, firm size and industry affiliation have no significant relationship with financial distress.Research limitationsDue to data availability, this study is limited to a sample of Swedish SMEs in five industries covering eight years. Further research could examine the generalizability of these findings by investigating other firms operating in other industries and other countries.Originality/valueThis study is the first to examine determinants of financial distress among SMEs operating in Sweden using data from a large-scale longitudinal cross-sectional database.

Sign in / Sign up

Export Citation Format

Share Document