Development of time series analysis tools applied to the investigation of seismograms for the discrimination between earthquakes and explosions

Project leaders

Luciano Telesca, Mohamed Rouai

Agreement

MAROCCO - CNRST - Centre National pour la Recherche Scientifique et Technique

Call

CNR/CNRST 2012-2013

Department

ICT

Thematic area

Engineering, ICT and technologies for energy and transportation

Status of the project

New

Research proposal

Discriminating earthquakes from explosions has been representing a challenging problem in the recent years. Toksöz et al. (1993) and Li et al. (1995) applied the empirical Green's function (EGF) method to teleseismic and regional waveform data from moderate to large seismic events (mb>5) and explosions in central Asia to test the reliability of the EGF method to determine their relative source time function (RSTF). It was found that a property of the RSTF, its time duration, discriminated earthquakes and explosions of similar magnitude, revealing that the RSTF time durations of earthquakes were about a factor of 10 longer than those of the nuclear explosions. Musil and Plešinger (1996) applied artificial neural networks (ANN) to discriminate microearthquakes from quarry blasts and mining blasts in West Bohemia earthquake swarm region. They seven amplitude and seven spectral parameters, automatically extracted from three-component broadband velocigrams of a single local seismic station for training several ANN configurations, and found that combinations of both spectral and amplitude parameters are more efficient discriminants than solely spectral parameters. Similarly, Del Pezzo et al. (2003) performed a neural network scheme to discriminate between volcano-tectonic earthquakes and underwater explosions in Phlegrean Fileds (Italy), obtaining a classification performance of 92%. Kim et al. (1997) analysed high-frequency regional records from small earthquakes (magnitude < 4.5) and chemical explosions with comparable magnitude in Russia near Kislovodsk. Their findings pointed out to the use of the spectral ratio Pg/Lg in the band 8 to 18 Hz as a good discriminant. Spectral discrimination between P-waves of quarry blasts and earthquakes recorded by the southern California seismic network (SCSN) between 2000 and 2005 was performed by Allmann et al. (2008) using the rms misfit to an ω-2 source model, revealing that quarry blasts spectra are not well fit by standard earthquake source models and exhibit anomalously high spectral fall-off rates compared to earthquakes of comparable moment magnitude. Very recently, nonlinear techniques based on the informational properties of time series (Fisher Information Measure and Shannon entropy) were applied to discriminate earthquakes from quarry blasts in Hungary (Telesca et al., 2011).
The Oud Zem phosphate mines in the Moroccan Meseta (Northeastern Morocco) provide a good test region to analyse recordings produced by ripple-fired explosions and to test methods of discrimination between seismograms produced by tectonic earthquakes and those produced by explosions. Seismograms of tectonic earthquakes occurred in the main seismic areas of Morocco will be obtained for performing the comparison. The seismogram data will be provided by the Moroccan Seismic MonitoringNetwork comprinsing 29 short period seismic sensors from which one of three components, 2 VBB stations and 24 accelerographs from which two interconnected networks. The installed seismographs are from Kinemetrics, SS1 sensors of short period type (1 Hz) and essentially of vertical components.
Therefore the intended activities, which aim at developing and applying robust and advanced method for the analysis of seismograms of earthquakes and explosions, include:  a)  creating of a common database seismograms of earthquakes and quarry blasts occurred in Morocco available for both teams;  b) developing of pre-processing techniques for the extraction of P- and S-waves;  c) developing of advanced methods of time series analysis to identify features linked with the nature of earthquakes and quarry blasts;  d) developing and integration of advanced nonlinear time series tools, combining fractal, multifractal, entropic, information-based and wavelet methods for the analysis of seismograms;  e) facilitating exchange visits of scientists as required to enhance the collaborative activities and generate research outputs;  g) supporting methodologically and technologically possible Ph.D students or young researchers;  h) disseminating the results of the collaboration.
The project combines the expertise of the two involved groups in investigating seismic data and the cooperation between them offers a real synergistic advantage of exchange of data and statistical/mathematical know-how.  In particular, the Italian team is involved in the development of advanced signal processing tools as shown by the quantity and quality of papers published in highly qualified peer-reviewed journals, while the Moroccan team has extensive and deep seismological experience and manage a large and very interesting seismic database. The cooperation between the two groups, merging their different expertise, will contribute to an effective upgrade of the knowledge in the topic of the project.
The expected results and deliverables of the project are:  1) Tools for the processing of seismograms.  2) Intermediate and final reports on the performed activities and obtained results.  3) Papers and abstracts submitted to international journals and conferences respectively with the acknowledgement of the CNR-CNRST bilateral agreement; 4) Seminars jointly organized in Italy and Morocco focused on the topics of the project.

Research goals

The specific objectives of the project are: 1) to investigate the time dynamics of the seismograms of natural earthquakes and quarry blasts occurred in Morocco, by means of advanced statistical time series tools (spectral, fractal, multifractal, entropic, information-based, wavelet, and other nonlinear tools); 2) to construct a set of discriminators between earthquakes and explosions; 3) to study the sensitivity/specificity of the discriminators; 4) to identify in the Moroccan seismic catalogue events that were misinterpreted as earthquakes on the base of the developed set of discriminators; 5) to disseminate preliminary and final results of the project in international conferences, publications.

Last update: 07/10/2024