Stavros Tolis - Academia.edu (original) (raw)
Papers by Stavros Tolis
The bulletin of the Seismological Society of America/Bulletin of the Seismological Society of America, Feb 13, 2024
Bulletin of the Geological Society of Greece, 2001
In this paper the application of the seismic tomography method for subsurface investigation, espe... more In this paper the application of the seismic tomography method for subsurface investigation, especially in the case of adit detection at depths between 30 and 80 meters is presented. The use of non destructive seismic sources as the mechanical hammer as well as seismic detonators were allowed seismic waves of dominant frequency between 200Έ250 Hz to be recorded. After the processing of seismic records and the subtraction of seismic noise by applying appropriate filters, the technique of non linear inversion was elaborated by using the advanced algorithm of J. Zhang and N. Toksoz (1998). This technique was applied in three borehole pairs that were drilled in the Kalogreza area. According to the obtained results there were no large subsurface adits detected. A small differentiation in seismic velocity (of the order of 300 m/s) near boreholes Bl-1 (mainly) and Bl-3, is due either to phasies change or to different physical condition of the material.
Proc. 2nd Int. Conference on Soil Structure Interaction in Urban Civil Engineering, 2002
The importance of the main geotechnical parameters affecting the results of two-dimensional plain... more The importance of the main geotechnical parameters affecting the results of two-dimensional plain strain tunnel analysis with the finite element method is presented. The effects on the surface settlement predictions of the strength and deformation parameters, the initial coefficient of earth pressure at rest, and the assumed relaxation factor of the rock mass before the application of the temporary support are examined for a typical configuration of the Athens metro tunnel. Settlements measured in the center of Athens are presented and combinations of parameters giving reasonable predictions are examined. The limitations and capabilities of back analysis are discussed.
Natural Hazards
We have compiled a new catalogue of earthquake fatalities for the world, covering the period 856 ... more We have compiled a new catalogue of earthquake fatalities for the world, covering the period 856 BC to March 2022, listing 2795 reports. We estimate that the reporting of fatal earthquakes is complete for events with more than 16 fatalities since 1927. The total number of fatalities recorded is 8,336,526. 117 countries have reported at least one earthquake with one fatality or more. 77 and 52 countries have reported more than 100 and 1000 earthquake fatalities, respectively. Caution has to be exercised in estimating what earthquake disasters are in store for a given country because the 95 year period of high quality recording is about an order of magnitude shorter than return times of great earthquakes. Nevertheless, we introduce the earthquake potency for a country, defined as the sum of recorded fatalities divided by the number of earthquakes that it took to accumulate them, which equals the average earthquake disaster size in a given country, in units of fatalities per event. Pot...
Natural Hazards, 2022
We have compiled a new catalogue of earthquake fatalities for the world, covering the period 856 ... more We have compiled a new catalogue of earthquake fatalities for the world, covering the period 856 BC to March 2022, listing 2795 reports. We estimate that the reporting of fatal earthquakes is complete for events with more than 16 fatalities since 1927. The total number of fatalities recorded is 8,336,526. 117 countries have reported at least one earthquake with one fatality or more. 77 and 52 countries have reported more than 100 and 1000 earthquake fatalities, respectively. Caution has to be exercised in estimating what earthquake disasters are in store for a given country because the 95 year period of high quality recording is about an order of magnitude shorter than return times of great earthquakes. Nevertheless, we introduce the earthquake potency for a country, defined as the sum of recorded fatalities divided by the number of earthquakes that it took to accumulate them, which equals the average earthquake disaster size in a given country, in units of fatalities per event. Potency is listed based on all known fatal earthquakes and also based on those since 1927. Both lists have their shortcomings, but provide estimates of what size of future earthquake disaster is likely in store for a particular country. For rescue purposes, it is important to realize that small earthquake, M 5 ± 0.5, can cause significant numbers of fatalities.
<p>Large earthquakes are unavoidable because globally the plate motions accumulate ... more <p>Large earthquakes are unavoidable because globally the plate motions accumulate stress, which leads to ruptures of the crustal rocks hundreds of kilometers long. In developed areas, this brings buildings to collapse, which injures and kills occupants. Potential rescuers are never well informed about the extent of an earthquake disaster because communication along the rupture is interrupted. We have documented that the underestimate of fatality numbers lasts for at least the crucial first few days, often for weeks. For earthquakes that cause thousands of casualties, the extent of underestimation is usually an order of magnitude. To reduce this uncertainty of whether help is required and how much, we have assembled a data set and constructed algorithms to estimate the number of fatalities and injured within&#160; an hour of any earthquake worldwide in the computer tool QLARM. Our estimates of the population and the makeup of the built environment comes from government and internet sources. For large earthquakes, the hypocenter and magnitude is calculated and distributed by the GEOFON group at the Geoforschungszentrum (GFZ) in Potsdam, Germany and the Geological Survey (USGS) in Golden, USA within 6 to 10 minutes. Based on this information, the QLARM operator responds with an estimate of the number of casualties within 30 minutes of the earthquake, on average. These estimates are available to anyone by email alerts without charge. Since 2003, the QLARM operator has issued more than 1,000 casualty alerts at any time of the day pro bono. The USGS delivers a similar service called PAGER, which is based on different data sets and algorithms. The two loss estimates are usually close, which should give governments and news organizations confidence that these alerts are to be taken seriously. The QLARM research group also publishes research results, estimating the likely numbers of future casualties in repeats of historical large earthquakes. In such efforts the QLARM group has discovered that, contrary to the general assumption, the rural population suffers more by an order of magnitude under very large earthquakes than the urban population. It is also clear that the poorer segment of the population in cities and countryside suffer more than the affluent members of society because the former&#8217;s houses are weaker and collapse more readily. To be even more useful, a worldwide data set of hospitals and schools is needed in order to provide first responders with locations and likely damage to these critical facilities. Crucially, reliable school location data would enable first responders to focus rescue efforts on&#160;schoolchildren who die beneath the rubble of their schools in the hundreds&#160;to thousands in large&#160;earthquakes. Unfortunately, such data are not available from official sources in most developing countries, and we are not aware of good alternatives. The data on schools in open data platforms such as OpenStreetMap is sporadic. UNICEF runs a global school mapping initiative, but we have been unable to obtain their assistance to date.</p>
That poor people live in buildings constructed with lower quality than those of affluent people i... more That poor people live in buildings constructed with lower quality than those of affluent people is a generally accepted fact. That buildings of low quality collapse in earthquake shaking more readily than those of high quality is also obvious. It follows that lower income families are more likely to die or be injured in earthquakes than well to do people. Here we estimate quantitatively what the difference in earthquake mortality may be as a function of affluence. Because mortality in earthquakes is much higher in developing countries than in highly advance ones, and the above assumptions are more correct in the former, we concentrate on the former. We have validated our algorithms and data sets available in the tool QLARM in detail in the following countries: China, India, Mexico, Iran and Greece. This means that the overall numbers of fatalities in earthquakes are estimated correctly within a factor of about 2.5 in these countries. That does not mean that we have separate knowledge of mortality in specific communities. Nevertheless, it allows us to propose that our technique to estimate fatalities is approximately correct in these countries. A critical and limiting assumption is that we model the distribution of buildings into classes of resistance to shaking in three classes only: villages (population < 2,000), towns (2,000 ≤ pop < 20,000) and cities (pop ≥ 20,000), according to the single publication on this topic. Subject to the aforementioned assumptions, we estimate that in countries like China, India and Iran the mortality in the rural population is 4 to 10 times larger than that in city dwellers. In Latin American countries the differences are in the range of factors of 2 to 4. Our data also suggest that in highly developed countries the mortality due to strong shaking is an order of magnitude less than in developing countries. We emphasize that the results presented here are based on approximate models for the built environment of settlements of different sizes. Therefore, our results are not the final ones. Quantitative information on building quality by communities should be developed to allow more precise estimates of the social bias in earthquake disasters. Nevertheless, based on the presented first order approximations of the higher earthquake risk for poor people, governments should consider means to better protect the population at the low end of the income curve.
Earthquake Hazard, Risk and Disasters, 2014
Journal of Earthquake Engineering, 1999
Recent developments in displacement-based design methodologies increased the need for reliable di... more Recent developments in displacement-based design methodologies increased the need for reliable displacement design spectra, especially in long periods. Design spectra proposed in Eurocode 8 are assessed, using recent attenuation relationships that predict response spectral ordinates based on European data, as well as five selected European strong-motion accelerograms. To identify possible trends in long period spectral displacements, several high quality digital recordings from the 1995 Hyogoken-Nanbu (Kobe) earthquake were collected and studied. Based on the differences recognised, possible modifications for the design spectrum to take them into account in the future revision of Eurocode 8 are proposed.
The bulletin of the Seismological Society of America/Bulletin of the Seismological Society of America, Feb 13, 2024
Bulletin of the Geological Society of Greece, 2001
In this paper the application of the seismic tomography method for subsurface investigation, espe... more In this paper the application of the seismic tomography method for subsurface investigation, especially in the case of adit detection at depths between 30 and 80 meters is presented. The use of non destructive seismic sources as the mechanical hammer as well as seismic detonators were allowed seismic waves of dominant frequency between 200Έ250 Hz to be recorded. After the processing of seismic records and the subtraction of seismic noise by applying appropriate filters, the technique of non linear inversion was elaborated by using the advanced algorithm of J. Zhang and N. Toksoz (1998). This technique was applied in three borehole pairs that were drilled in the Kalogreza area. According to the obtained results there were no large subsurface adits detected. A small differentiation in seismic velocity (of the order of 300 m/s) near boreholes Bl-1 (mainly) and Bl-3, is due either to phasies change or to different physical condition of the material.
Proc. 2nd Int. Conference on Soil Structure Interaction in Urban Civil Engineering, 2002
The importance of the main geotechnical parameters affecting the results of two-dimensional plain... more The importance of the main geotechnical parameters affecting the results of two-dimensional plain strain tunnel analysis with the finite element method is presented. The effects on the surface settlement predictions of the strength and deformation parameters, the initial coefficient of earth pressure at rest, and the assumed relaxation factor of the rock mass before the application of the temporary support are examined for a typical configuration of the Athens metro tunnel. Settlements measured in the center of Athens are presented and combinations of parameters giving reasonable predictions are examined. The limitations and capabilities of back analysis are discussed.
Natural Hazards
We have compiled a new catalogue of earthquake fatalities for the world, covering the period 856 ... more We have compiled a new catalogue of earthquake fatalities for the world, covering the period 856 BC to March 2022, listing 2795 reports. We estimate that the reporting of fatal earthquakes is complete for events with more than 16 fatalities since 1927. The total number of fatalities recorded is 8,336,526. 117 countries have reported at least one earthquake with one fatality or more. 77 and 52 countries have reported more than 100 and 1000 earthquake fatalities, respectively. Caution has to be exercised in estimating what earthquake disasters are in store for a given country because the 95 year period of high quality recording is about an order of magnitude shorter than return times of great earthquakes. Nevertheless, we introduce the earthquake potency for a country, defined as the sum of recorded fatalities divided by the number of earthquakes that it took to accumulate them, which equals the average earthquake disaster size in a given country, in units of fatalities per event. Pot...
Natural Hazards, 2022
We have compiled a new catalogue of earthquake fatalities for the world, covering the period 856 ... more We have compiled a new catalogue of earthquake fatalities for the world, covering the period 856 BC to March 2022, listing 2795 reports. We estimate that the reporting of fatal earthquakes is complete for events with more than 16 fatalities since 1927. The total number of fatalities recorded is 8,336,526. 117 countries have reported at least one earthquake with one fatality or more. 77 and 52 countries have reported more than 100 and 1000 earthquake fatalities, respectively. Caution has to be exercised in estimating what earthquake disasters are in store for a given country because the 95 year period of high quality recording is about an order of magnitude shorter than return times of great earthquakes. Nevertheless, we introduce the earthquake potency for a country, defined as the sum of recorded fatalities divided by the number of earthquakes that it took to accumulate them, which equals the average earthquake disaster size in a given country, in units of fatalities per event. Potency is listed based on all known fatal earthquakes and also based on those since 1927. Both lists have their shortcomings, but provide estimates of what size of future earthquake disaster is likely in store for a particular country. For rescue purposes, it is important to realize that small earthquake, M 5 ± 0.5, can cause significant numbers of fatalities.
<p>Large earthquakes are unavoidable because globally the plate motions accumulate ... more <p>Large earthquakes are unavoidable because globally the plate motions accumulate stress, which leads to ruptures of the crustal rocks hundreds of kilometers long. In developed areas, this brings buildings to collapse, which injures and kills occupants. Potential rescuers are never well informed about the extent of an earthquake disaster because communication along the rupture is interrupted. We have documented that the underestimate of fatality numbers lasts for at least the crucial first few days, often for weeks. For earthquakes that cause thousands of casualties, the extent of underestimation is usually an order of magnitude. To reduce this uncertainty of whether help is required and how much, we have assembled a data set and constructed algorithms to estimate the number of fatalities and injured within&#160; an hour of any earthquake worldwide in the computer tool QLARM. Our estimates of the population and the makeup of the built environment comes from government and internet sources. For large earthquakes, the hypocenter and magnitude is calculated and distributed by the GEOFON group at the Geoforschungszentrum (GFZ) in Potsdam, Germany and the Geological Survey (USGS) in Golden, USA within 6 to 10 minutes. Based on this information, the QLARM operator responds with an estimate of the number of casualties within 30 minutes of the earthquake, on average. These estimates are available to anyone by email alerts without charge. Since 2003, the QLARM operator has issued more than 1,000 casualty alerts at any time of the day pro bono. The USGS delivers a similar service called PAGER, which is based on different data sets and algorithms. The two loss estimates are usually close, which should give governments and news organizations confidence that these alerts are to be taken seriously. The QLARM research group also publishes research results, estimating the likely numbers of future casualties in repeats of historical large earthquakes. In such efforts the QLARM group has discovered that, contrary to the general assumption, the rural population suffers more by an order of magnitude under very large earthquakes than the urban population. It is also clear that the poorer segment of the population in cities and countryside suffer more than the affluent members of society because the former&#8217;s houses are weaker and collapse more readily. To be even more useful, a worldwide data set of hospitals and schools is needed in order to provide first responders with locations and likely damage to these critical facilities. Crucially, reliable school location data would enable first responders to focus rescue efforts on&#160;schoolchildren who die beneath the rubble of their schools in the hundreds&#160;to thousands in large&#160;earthquakes. Unfortunately, such data are not available from official sources in most developing countries, and we are not aware of good alternatives. The data on schools in open data platforms such as OpenStreetMap is sporadic. UNICEF runs a global school mapping initiative, but we have been unable to obtain their assistance to date.</p>
That poor people live in buildings constructed with lower quality than those of affluent people i... more That poor people live in buildings constructed with lower quality than those of affluent people is a generally accepted fact. That buildings of low quality collapse in earthquake shaking more readily than those of high quality is also obvious. It follows that lower income families are more likely to die or be injured in earthquakes than well to do people. Here we estimate quantitatively what the difference in earthquake mortality may be as a function of affluence. Because mortality in earthquakes is much higher in developing countries than in highly advance ones, and the above assumptions are more correct in the former, we concentrate on the former. We have validated our algorithms and data sets available in the tool QLARM in detail in the following countries: China, India, Mexico, Iran and Greece. This means that the overall numbers of fatalities in earthquakes are estimated correctly within a factor of about 2.5 in these countries. That does not mean that we have separate knowledge of mortality in specific communities. Nevertheless, it allows us to propose that our technique to estimate fatalities is approximately correct in these countries. A critical and limiting assumption is that we model the distribution of buildings into classes of resistance to shaking in three classes only: villages (population < 2,000), towns (2,000 ≤ pop < 20,000) and cities (pop ≥ 20,000), according to the single publication on this topic. Subject to the aforementioned assumptions, we estimate that in countries like China, India and Iran the mortality in the rural population is 4 to 10 times larger than that in city dwellers. In Latin American countries the differences are in the range of factors of 2 to 4. Our data also suggest that in highly developed countries the mortality due to strong shaking is an order of magnitude less than in developing countries. We emphasize that the results presented here are based on approximate models for the built environment of settlements of different sizes. Therefore, our results are not the final ones. Quantitative information on building quality by communities should be developed to allow more precise estimates of the social bias in earthquake disasters. Nevertheless, based on the presented first order approximations of the higher earthquake risk for poor people, governments should consider means to better protect the population at the low end of the income curve.
Earthquake Hazard, Risk and Disasters, 2014
Journal of Earthquake Engineering, 1999
Recent developments in displacement-based design methodologies increased the need for reliable di... more Recent developments in displacement-based design methodologies increased the need for reliable displacement design spectra, especially in long periods. Design spectra proposed in Eurocode 8 are assessed, using recent attenuation relationships that predict response spectral ordinates based on European data, as well as five selected European strong-motion accelerograms. To identify possible trends in long period spectral displacements, several high quality digital recordings from the 1995 Hyogoken-Nanbu (Kobe) earthquake were collected and studied. Based on the differences recognised, possible modifications for the design spectrum to take them into account in the future revision of Eurocode 8 are proposed.