University of Malta
 

2000-2006
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2000-2001

 

Student: Tania Scerri

 

Title: Duration Magnitude  Scale and Analysis of Seismicity around the Maltese Islands

 

Abstract: The aim of this project was to establish the duration magnitude scale for earthquakes in the Central Mediterranean recorded at station WDD, Malta, and to study seismic activity in the region surrounding the Maltese Islands. Since 1983, seismic instrumentation in Malta had seen a growth, enabling useful data sets to unravel very important features of this region.

 

Magnitude is an experimentally determined measure of the size of an earthquake. The duration magnitude utilises the coda length to establish the magnitude formula. It is the main aim of this project to empirically determine the duration magnitude formula for the Sicily Channel. To derive such a scale a representative group of shocks is essential. The seismic events chosen are recorded in Malta and also located by I.N.G. (Instituto Nazionale di Geofisica). The equation is determined empirically by the method of least square fitting. In addition, the relationship between the earthquake size and the frequency of occurrence proposed by Richter (1958) was also achieved empirically for the Sicily Channel. Furthermore, the implication of swarm activities in the Pantelleria Rift was discussed. The duration magnitude suffers from a shortcoming in that it is applied only to short distance range. However, it is considered sufficient and convenient for the purpose of this study in the Central Mediterranean.

 

 


2002 - 2003

 

Student: Jesmond Agius

 

Title: Discrimination between Quarry Blasts and Micro Earthquakes around the Maltese Islands

 

Abstract: The aim of this project was to establish criteria for determining between quarry blasts and micro earthquakes in the region of the Maltese Islands. On the Maltese Islands, quarry blasts and micro earthquakes occur in a region with complicated tectonics. Therefore correct event identification,  preferably based on a simple method that can be applied on a routine basis, is essential for accurate and detailed seismotectonic studies.

 

A dataset, containing quarry blasts and microearthquake events recorded on the WDD seismograph were selected. The quarry blasts were identified by confirmation with the Malta Environment and Planning Authority (MEPA). A number of characteristics of all the waveforms were studied, such as local/duration magnitude ratios, spectral features etc. in order to identify which characteristics provided a clear distinction between the two types of events.

 

It was established that discrimination between the two types of local events is possible by using MD/ML ratios (duration to local magnitude) as well as by Lg/Pg ratios. But it is more practical to use MD/ML ratios for discriminating between quarry blasts and microearthquakes, since this requires less accuracies and procedures than by using the Lg/Pg ratio method.

 

 


2003 - 2004

 

Student: Matthew Agius

 

Title: Data Acquisition System for a Seismic

 

Abstract:  Any type of detailed research or scientific study of huge environments such as our planet Earth would require sensitive and accurate instruments. More often then not, the most significant events occur unexpectedly and to capture such occurrences a dedicated system is required to be in continuous operation with the minimum human supervision. In this project, an automated data collection system has been designed, constructed and put to work. The system takes analogue voltage readings from a three component ground motion seismometers, converts them to a digital form and saves the result on disk.

 

The system is designed around three analogue-to-digital converters with a 24-bit resolution and a maximum sampling rate of 100Hz. The samples are time-stamped with a signal that is attained from a Global Positioning System (GPS) receiver.  A dedicated processor handles the raw data collection, and transfers the data to a PC for storage. Software written particularly for this purpose provides a user interface as well as a triggering facility so that only significant events are stored, thus saving disk space.  The data on the PC can then be accessed using standard software and networking facilities.

 


 


2005-2006

 

Student: Ingrid Borg

 

Title: Analysis of Seismic Activity around the Maltese Islands, and the use of Waveform Cross-Correlation Technique

 

Abstract:  A continuation of the study of seismic activity around the Maltese Islands was carried out. A total of 44 earthquakes occurring between 2004 and 2005 were identified from digital recordings of Wied Dalam seismograph. Their approximate distance from Wied Dalam station (WDD) and magnitude were calculated and an attempt was made in investigating whether seismic swarm activity on the offshore faults around the Maltese Islands are still occurring. The seismic activity for this period was compared to that of previous years analysed in other studies. The location of small seismic events, like the ones considered here, is very difficult since not all of the events recorded on WDD are recorded on stations in Sicily and Tunisia.

 

A study was also made of the possibility of using the waveform cross-correlation function to identify events in the same swarm. The cross-correlation function of pairs of events having the same epicentral distance was calculated using the PITSA software. It was found that some pairs of events occurring very close together in time had very high cross-correlation (greater than 0.7) indicating that similar pairs were occurring on the same fault and presumably having the same fault mechanism. For other event pairs however, the cross-correlation was low, even for earthquakes known to be from the same region.

 

In general, the correlation between waveforms is sustained only in certain cases and therefore cannot be used as a routine tool is associating events to the same source.

 

Calendar
Notices
Outstanding Academic Title
The book "Earthquakes and their Impact on Society" has been selected by Choice magazine as"Outstanding Academic title" for 2016 
Participation at AGU
Dr Sebastiano D’Amico and Ms Daniela Farrugia (Department of Geosciences) have participated in the American Geophysical Union (AGU) Fall Meeting held in San Francisco (USA) from 10th to 15th December 2016.
ESC 2018
Valletta to host 36th General Assembly of the European Seismological Commission in 2018
 
 
Last Updated: 4 November 2015

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