Maximiliano Astroza - Academia.edu (original) (raw)
Papers by Maximiliano Astroza
En este trabajo se entrega una herramienta para determinar la vulnerabilidad sísmica de los edifi... more En este trabajo se entrega una herramienta para determinar la vulnerabilidad sísmica de los edificios de albañilería confinada de tres y cuatro pisos. Con este propósito se realiza una calibración del índice de vulnerabilidad de la metodología desarrollada por el G.N.D.T. (Gruppo Nazionale per la Difensa dai Terremoti -Italia), incorporando elementos de juicio de acuerdo con las características que determinan la respuesta sísmica de estas estructuras. Además se establece una relación entre los valores que resultan de este índice con los niveles de daño que pueden ocurrir durante un terremoto de subducción del tipo interplaca como el ocurrido en Chile el 3 de marzo de 1985. Para realizar el estudio se utilizaron 24 edificios de 3 y 4 pisos construidos para los programas de viviendas sociales; la muestra se puede considerar que es representativa de los edificios de albañilería confinada construidos en Chile y en varios países de la costa oeste de Latinoamérica.
This paper shows that attenuation formula for peak ground acceleration (PGA) for Chile subduction... more This paper shows that attenuation formula for peak ground acceleration (PGA) for Chile subduction zone, derived from a homogeneous database for thrust interplate and inslab of intermediate depth earthquakes recorded on 'hard rock' and 'rock and hard soil', give systematically higher values than universal formulas proposed for subduction zones. Also PGA Chilean values are higher than values for Mexico and Cascadia subduction zone values. Criterion of homogeneous database is defined in order to obtain PGA attenuation formulas with high correlation coefficients. Comparison of MMI attenuation formulas for Chile, Mexico and Cascadia subductions is also made. The main conclusion is not possible to obtain universal attenuation formula for PGA and MMI for subduction zones and attenuation formulas can be quite different for each American subduction zone. Formulas look to depend of the age of the converging tectonic plate, convergence velocity, stress drop, among other factors...
Tectonophysics, 2002
The 1943 Illapel seismic gap, central Chile (30 -32BS), was partially reactivated in 1997 -1998 b... more The 1943 Illapel seismic gap, central Chile (30 -32BS), was partially reactivated in 1997 -1998 by two distinct seismic clusters. On July 1997, a swarm of offshore earthquakes occurred on the northern part of the gap, along the coupled zone between Nazca and South American plates. Most of the focal mechanisms computed for these earthquakes show thrust faulting solutions. The July 1997 swarm was followed on October 15, 1997 by the Punitaqui main event (Mw = 7.1), which destroyed the majority of adobe constructions in Punitaqui village and its environs. The main event focal mechanism indicates normal faulting with the more vertical plane considered as the active fault. This event is located inland at 68-km depth and it is assumed to be within the oceanic subducted plate, as are most of the more destructive Chilean seismic events. Aftershocks occurred mainly to the north of the Punitaqui mainshock location, in the central-eastern part of the Illapel seismic gap, but at shallower depths, with the two largest showing thrust focal mechanisms. The seismicity since 1964 has been relocated with a master event technique and a Joint Hypocenter Determination (JHD) algorithm, using teleseismic and regional data, along with aftershock data recorded by a temporary local seismic network and strong motion stations. These data show that the 1997 seismic clusters occurred at zones within the Illapel gap where low seismicity was observed during the considered time period. The analysis of P and T axis directions along the subduction zone, using the Harvard Centroid Moment Tensor solutions since 1977, shows that the oceanic slab is in a downdip extensional regime. In contrast, the Punitaqui mainshock is related to compression resulting from the flexure of the oceanic plate, which becomes subhorizontal at depths of about 100 km. Analog strong motion data of the Punitaqui main event show that the greatest accelerations are on the horizontal components. The highest amplitude spectra of the acceleration is in the frequency band 2.5 -10 Hz, in agreement with the energy band responsible for the collapsed adobe constructions. The isoseismal map derived from the distribution of observed damage show that a high percentage of destruction is due to the proximity of the mainshock, the poor quality of adobe houses and probably local site amplification effects. D
Physics of the Earth and Planetary Interiors, 2009
Journal of Structural Engineering, 1996
ABSTRACT Seismic design provisions, including the Chilean seismic code, prescribe seismic design ... more ABSTRACT Seismic design provisions, including the Chilean seismic code, prescribe seismic design forces by reducing a linear elastic response spectra using a response modification factor. The codes also estimate expected maximum inelastic displacement that may occur during a severe earthquake, by amplifying the elastic displacement computed from the design seismic forces by a displacement amplification factor, In this paper, the seismic force reduction factor R(w) and displacement amplification factor Cd ate computed for typical confined masonry buildings, comparing base shear and first-story drift that develop in the structure when linear or nonlinear behavior is adopted. The computations are performed after analyzing several three and four story buildings, These buildings Were subjected to the action of a number of earthquakes records obtained in Chile on March 3, 1985 and in Mexico on Sept. 19, 1985. The R(w) factor, evaluated fat this type of building, depends bath on the structure's wall density and on the source mechanism of the earthquake; in contrast to most code recommendations, the ratio of R(w)/C-d obtained is less than 1.
Journal of Performance of Constructed Facilities, 2004
Masonry is the most used construction material, especially for residential dwellings built in all... more Masonry is the most used construction material, especially for residential dwellings built in all regions of Chile, up to four stories high. The masonry wall's reinforcement of these buildings can be classified into three types: confined, reinforced and hybrid. Although buildings with confined masonry walls have limited shear strength and ductility, they have demonstrated acceptable seismic behavior. Experience for buildings with the other two types of reinforcement has been different; during the 1985 Llolleo earthquake several buildings had severe damage due to design and construction deficiencies. In this paper a description of key structural features, construction process, seismic resilient features and deficiencies of masonry housing types used in government-subsidized low-income dwellings is provided. In addition, various seismic vulnerability indices that characterize their seismic behavior are calculated. The evolution over time of such indices shows that nowadays a large amount of buildings are likely to be damaged after a severe earthquake.
Journal of Earthquake Engineering, 2008
On the 4th of September 1958, a sequence of 3 earthquakes of magnitude 6.76.9 struck the Andean ... more On the 4th of September 1958, a sequence of 3 earthquakes of magnitude 6.76.9 struck the Andean Main Cordillera at the latitude of Santiago, Central Chile. The quakes were preceded by a magni-tude 6.0 foreshock one week earlier. This seismic sequence provided the ...
Earthquake Spectra, 2012
The 2010 Maule earthquake is one of the largest events ever recorded with modern instruments. We ... more The 2010 Maule earthquake is one of the largest events ever recorded with modern instruments. We used the continuous GPS (cGPS) records to invert for the kinematic rupture process using an elliptical sub-patch approximation. In agreement with previous inversions, the largest slip is found in the northern part of the rupture zone. By cross-correlating signals from cGPS and strong motion records (SM) located in the northern part of the rupture zone, we identified two distinct seismic pulses. Using the arrival time of these pulses, we propose a short-period (<20 s) rupture process, the zone where these pulses are generated is situated near 35.5°S, in agreement with the area with the highest seismic slip and maximum observed intensity. Finally, we compare the strong motion records at the same sites for the 1985 M w 8 Valparaíso earthquake and the Maule earthquake. We found that spectral contents and duration of the records of these two events were very similar. Thus, at least in the northern part of the rupture, the Maule earthquake radiated high frequency waves like an M w 8 earthquake.
Earthquake Spectra, 2012
ABSTRACT Engineered masonry, namely reinforced and confined masonry, has been widely used for hou... more ABSTRACT Engineered masonry, namely reinforced and confined masonry, has been widely used for housing construction in Chile over the last few decades. Most one- and two-story single-family masonry dwellings did not experience any damage due to the 27 February 2010 Maule earthquake, with the exception of a few dwellings of pre-1970 vintage, which suffered moderate damage. A similar statement can be made for three- and four-story confined masonry buildings: a large majority of buildings remained undamaged. However, several reinforced and partially confined three- and four-story masonry buildings suffered extensive damage, and two three-story partially confined buildings collapsed. The key damage patterns and the causes of damage are discussed in the paper. The extent of damage observed in the field was correlated with calculated vulnerability indices, and relevant recommendations were made related to the design and construction practices. [DOI: 10.1193/1.4000040]
The 2010 Maule earthquake is one of the largest events ever recorded with modern instruments. We ... more The 2010 Maule earthquake is one of the largest events ever recorded with modern instruments. We used the continuous GPS (cGPS) records to invert for the kinematic rupture process using an elliptical sub-patch approximation. In agreement with previous inversions, the largest slip is found in the northern part of the rupture zone. By cross-correlating signals from cGPS and strong motion records (SM) located in the northern part of the rupture zone, we identified two distinct seismic pulses. Using the arrival time of these pulses, we propose a short-period (<20 s) rupture process, the zone where these pulses are generated is situated near 35.5°S, in agreement with the area with the highest seismic slip and maximum observed intensity. Finally, we compare the strong motion records at the same sites for the 1985 M w 8 Valparaíso earthquake and the Maule earthquake. We found that spectral contents and duration of the records of these two events were very similar. Thus, at least in the northern part of the rupture, the Maule earthquake radiated high frequency waves like an M w 8 earthquake.
Moroni Yadlin and Maximiliano Astoza of Universidad de Chile, Santiago visited the earthquake-aff... more Moroni Yadlin and Maximiliano Astoza of Universidad de Chile, Santiago visited the earthquake-affected area, including Santiago, Rancagua, Cauquenes, Talca, Constitución, Iloca, Lolol, and Santa Cruz. The visit took place from July 3 to 10, 2010. This report summarizes the key observations related to performance of confined masonry buildings in the earthquake-affected area. A companion slide show is posted on the web site www.confinedmasonry.org.
En este trabajo se entrega una herramienta para determinar la vulnerabilidad sísmica de los edifi... more En este trabajo se entrega una herramienta para determinar la vulnerabilidad sísmica de los edificios de albañilería confinada de tres y cuatro pisos. Con este propósito se realiza una calibración del índice de vulnerabilidad de la metodología desarrollada por el G.N.D.T. (Gruppo Nazionale per la Difensa dai Terremoti -Italia), incorporando elementos de juicio de acuerdo con las características que determinan la respuesta sísmica de estas estructuras. Además se establece una relación entre los valores que resultan de este índice con los niveles de daño que pueden ocurrir durante un terremoto de subducción del tipo interplaca como el ocurrido en Chile el 3 de marzo de 1985. Para realizar el estudio se utilizaron 24 edificios de 3 y 4 pisos construidos para los programas de viviendas sociales; la muestra se puede considerar que es representativa de los edificios de albañilería confinada construidos en Chile y en varios países de la costa oeste de Latinoamérica.
This paper shows that attenuation formula for peak ground acceleration (PGA) for Chile subduction... more This paper shows that attenuation formula for peak ground acceleration (PGA) for Chile subduction zone, derived from a homogeneous database for thrust interplate and inslab of intermediate depth earthquakes recorded on 'hard rock' and 'rock and hard soil', give systematically higher values than universal formulas proposed for subduction zones. Also PGA Chilean values are higher than values for Mexico and Cascadia subduction zone values. Criterion of homogeneous database is defined in order to obtain PGA attenuation formulas with high correlation coefficients. Comparison of MMI attenuation formulas for Chile, Mexico and Cascadia subductions is also made. The main conclusion is not possible to obtain universal attenuation formula for PGA and MMI for subduction zones and attenuation formulas can be quite different for each American subduction zone. Formulas look to depend of the age of the converging tectonic plate, convergence velocity, stress drop, among other factors...
Tectonophysics, 2002
The 1943 Illapel seismic gap, central Chile (30 -32BS), was partially reactivated in 1997 -1998 b... more The 1943 Illapel seismic gap, central Chile (30 -32BS), was partially reactivated in 1997 -1998 by two distinct seismic clusters. On July 1997, a swarm of offshore earthquakes occurred on the northern part of the gap, along the coupled zone between Nazca and South American plates. Most of the focal mechanisms computed for these earthquakes show thrust faulting solutions. The July 1997 swarm was followed on October 15, 1997 by the Punitaqui main event (Mw = 7.1), which destroyed the majority of adobe constructions in Punitaqui village and its environs. The main event focal mechanism indicates normal faulting with the more vertical plane considered as the active fault. This event is located inland at 68-km depth and it is assumed to be within the oceanic subducted plate, as are most of the more destructive Chilean seismic events. Aftershocks occurred mainly to the north of the Punitaqui mainshock location, in the central-eastern part of the Illapel seismic gap, but at shallower depths, with the two largest showing thrust focal mechanisms. The seismicity since 1964 has been relocated with a master event technique and a Joint Hypocenter Determination (JHD) algorithm, using teleseismic and regional data, along with aftershock data recorded by a temporary local seismic network and strong motion stations. These data show that the 1997 seismic clusters occurred at zones within the Illapel gap where low seismicity was observed during the considered time period. The analysis of P and T axis directions along the subduction zone, using the Harvard Centroid Moment Tensor solutions since 1977, shows that the oceanic slab is in a downdip extensional regime. In contrast, the Punitaqui mainshock is related to compression resulting from the flexure of the oceanic plate, which becomes subhorizontal at depths of about 100 km. Analog strong motion data of the Punitaqui main event show that the greatest accelerations are on the horizontal components. The highest amplitude spectra of the acceleration is in the frequency band 2.5 -10 Hz, in agreement with the energy band responsible for the collapsed adobe constructions. The isoseismal map derived from the distribution of observed damage show that a high percentage of destruction is due to the proximity of the mainshock, the poor quality of adobe houses and probably local site amplification effects. D
Physics of the Earth and Planetary Interiors, 2009
Journal of Structural Engineering, 1996
ABSTRACT Seismic design provisions, including the Chilean seismic code, prescribe seismic design ... more ABSTRACT Seismic design provisions, including the Chilean seismic code, prescribe seismic design forces by reducing a linear elastic response spectra using a response modification factor. The codes also estimate expected maximum inelastic displacement that may occur during a severe earthquake, by amplifying the elastic displacement computed from the design seismic forces by a displacement amplification factor, In this paper, the seismic force reduction factor R(w) and displacement amplification factor Cd ate computed for typical confined masonry buildings, comparing base shear and first-story drift that develop in the structure when linear or nonlinear behavior is adopted. The computations are performed after analyzing several three and four story buildings, These buildings Were subjected to the action of a number of earthquakes records obtained in Chile on March 3, 1985 and in Mexico on Sept. 19, 1985. The R(w) factor, evaluated fat this type of building, depends bath on the structure's wall density and on the source mechanism of the earthquake; in contrast to most code recommendations, the ratio of R(w)/C-d obtained is less than 1.
Journal of Performance of Constructed Facilities, 2004
Masonry is the most used construction material, especially for residential dwellings built in all... more Masonry is the most used construction material, especially for residential dwellings built in all regions of Chile, up to four stories high. The masonry wall's reinforcement of these buildings can be classified into three types: confined, reinforced and hybrid. Although buildings with confined masonry walls have limited shear strength and ductility, they have demonstrated acceptable seismic behavior. Experience for buildings with the other two types of reinforcement has been different; during the 1985 Llolleo earthquake several buildings had severe damage due to design and construction deficiencies. In this paper a description of key structural features, construction process, seismic resilient features and deficiencies of masonry housing types used in government-subsidized low-income dwellings is provided. In addition, various seismic vulnerability indices that characterize their seismic behavior are calculated. The evolution over time of such indices shows that nowadays a large amount of buildings are likely to be damaged after a severe earthquake.
Journal of Earthquake Engineering, 2008
On the 4th of September 1958, a sequence of 3 earthquakes of magnitude 6.76.9 struck the Andean ... more On the 4th of September 1958, a sequence of 3 earthquakes of magnitude 6.76.9 struck the Andean Main Cordillera at the latitude of Santiago, Central Chile. The quakes were preceded by a magni-tude 6.0 foreshock one week earlier. This seismic sequence provided the ...
Earthquake Spectra, 2012
The 2010 Maule earthquake is one of the largest events ever recorded with modern instruments. We ... more The 2010 Maule earthquake is one of the largest events ever recorded with modern instruments. We used the continuous GPS (cGPS) records to invert for the kinematic rupture process using an elliptical sub-patch approximation. In agreement with previous inversions, the largest slip is found in the northern part of the rupture zone. By cross-correlating signals from cGPS and strong motion records (SM) located in the northern part of the rupture zone, we identified two distinct seismic pulses. Using the arrival time of these pulses, we propose a short-period (<20 s) rupture process, the zone where these pulses are generated is situated near 35.5°S, in agreement with the area with the highest seismic slip and maximum observed intensity. Finally, we compare the strong motion records at the same sites for the 1985 M w 8 Valparaíso earthquake and the Maule earthquake. We found that spectral contents and duration of the records of these two events were very similar. Thus, at least in the northern part of the rupture, the Maule earthquake radiated high frequency waves like an M w 8 earthquake.
Earthquake Spectra, 2012
ABSTRACT Engineered masonry, namely reinforced and confined masonry, has been widely used for hou... more ABSTRACT Engineered masonry, namely reinforced and confined masonry, has been widely used for housing construction in Chile over the last few decades. Most one- and two-story single-family masonry dwellings did not experience any damage due to the 27 February 2010 Maule earthquake, with the exception of a few dwellings of pre-1970 vintage, which suffered moderate damage. A similar statement can be made for three- and four-story confined masonry buildings: a large majority of buildings remained undamaged. However, several reinforced and partially confined three- and four-story masonry buildings suffered extensive damage, and two three-story partially confined buildings collapsed. The key damage patterns and the causes of damage are discussed in the paper. The extent of damage observed in the field was correlated with calculated vulnerability indices, and relevant recommendations were made related to the design and construction practices. [DOI: 10.1193/1.4000040]
The 2010 Maule earthquake is one of the largest events ever recorded with modern instruments. We ... more The 2010 Maule earthquake is one of the largest events ever recorded with modern instruments. We used the continuous GPS (cGPS) records to invert for the kinematic rupture process using an elliptical sub-patch approximation. In agreement with previous inversions, the largest slip is found in the northern part of the rupture zone. By cross-correlating signals from cGPS and strong motion records (SM) located in the northern part of the rupture zone, we identified two distinct seismic pulses. Using the arrival time of these pulses, we propose a short-period (<20 s) rupture process, the zone where these pulses are generated is situated near 35.5°S, in agreement with the area with the highest seismic slip and maximum observed intensity. Finally, we compare the strong motion records at the same sites for the 1985 M w 8 Valparaíso earthquake and the Maule earthquake. We found that spectral contents and duration of the records of these two events were very similar. Thus, at least in the northern part of the rupture, the Maule earthquake radiated high frequency waves like an M w 8 earthquake.
Moroni Yadlin and Maximiliano Astoza of Universidad de Chile, Santiago visited the earthquake-aff... more Moroni Yadlin and Maximiliano Astoza of Universidad de Chile, Santiago visited the earthquake-affected area, including Santiago, Rancagua, Cauquenes, Talca, Constitución, Iloca, Lolol, and Santa Cruz. The visit took place from July 3 to 10, 2010. This report summarizes the key observations related to performance of confined masonry buildings in the earthquake-affected area. A companion slide show is posted on the web site www.confinedmasonry.org.