Estudio estadístico de la dirección de esfuerzos principales en terremotos

Tesis Univ. Complutense de Madrid, 1982.Depto. de Física de la Tierra y AstrofísicaFac. de Ciencias FísicasTRUEProQuestpu

Estudio estadístico de la dirección de esfuerzos principales en terremotos

Tesis Univ. Complutense de Madrid, 1982.Depto. de Física de la Tierra y AstrofísicaFac. de Ciencias FísicasTRUEProQuestpu

From strike-slip to reverse reactivation: The Crevillente Fault System and seismicity in the Bullas-Mula area (Betic Cordillera, SE Spain)

Several major N80ºE faults occur in the Bullas-Mula area (SE Spain). These faults and the numerous thrust slices of the Sierra de Ricote can be related to the movements of the Crevillente (or Cadiz-Alicante) fault system, which causes the westward displacement of the Betic Internal Zone and part of the External Zone. These faults moved with dextral strike-slip from Late Burdigalian to Early Tortonian. From this time on, the σ1 position changed from a WNW-ESE direction to approximately N-S, giving rise to movements with a new reverse character. The focal mechanisms of the 1999 Mula earthquakes indicate a N80ºE nodal plane, and their pressure axes also coincide with the σ1 direction existing from the Late Miocene and deduced from mesotectonic analysis at many points of the region. There is also good coincidence between their epicentral position and the fault traces. The Bullas earthquakes that occurred in 2002 are not directly related to the Crevillente faults, although their stress-pressure axes coincide with the σ1 direction reported there

A permanent submarine observatory in alboran and the long term OBS fomar Network. news.

Peer Reviewe

Four Years of Earthquake Early Warning in Southern Iberia: 2016-2019

The performance of an earthquake early warning system (EEWS) for southern Iberia during the period of 2016-2019 is analyzed. The software PRESTo (PRobabilistic and Evolutionary early warning SysTem; the University of Naples Federico II, Italy) operating at the Universidad Complutense de Madrid has detected 728 events (2 < M-w < 6.3), with 680 earthquakes occurring in southern Iberia. Differences between the EEWS origin time and epicenter and those of the Instituto Geografico Nacional (IGN) catalog are less than 2 s and 20 km, respectively, for 70% of the detected earthquakes. The main differences correspond to the EEWS magnitude that is underestimated for earthquakes that occurred at the west of the Gibraltar Strait (M-w differences larger than 0.3 for 70%). To solve this problem, several relationships have been tested, and a modification to those that currently use PRESTo is proposed. Other improvements, such as to densify the network or to use 3D Earth models, are proposed to decrease the time needed to issue the alert and avoid the false alerts (19 events over a total of 728 events). The EEWS has estimated the depth for 680 events and compared to those from the IGN (491 events). The performance of PRESTo during the 2020-2021 Granada swarm is analyzed. The hypocentral locations for the three largest earthquakes are close to those from the IGN (differences from 1 to 7 km for the epicenter and 0 s for the time origin), although there are some differences in their magnitude estimations that varies from 0.2 to 0.5. The PRESTo first times are 17, 25, and 41 s after the origin time. This study shows that the actual PRESTo EEWS configured for the southern Iberia may generate effective warnings despite the low seismicity rate in this region. To decrease the warning time, the geometry and density of the seismic network must be improved together with the use of 3D Earth models and on-site system approaches.</p

A Threshold-Based Earthquake Early-Warning System for Offshore Events in Southern Iberia

The south of the Iberian Peninsula is a region situated at the convergence of the Eurasian and African plates. This region experiences large earthquakes with a long separation in time, the best known of which is the great 1755 Lisbon Earthquake (i.e., maximum macroseismic intensity, Imax=X), which occurred SW of San Vicente Cape (SW Iberian Peninsula). The high risk of damaging earthquakes has recently lead Carranza et al. (2013) to investigate the feasibility of an EEWS in this region. The analysis of the geometrical situation between the Iberian seismic networks and the San Vicente Cape area led the authors to conclude that a threshold-based approach, which would not require the real-time location of the earthquake, might be the best option for EEWS in SW Iberia. The current work explores this hypothesis, and proposes a new EEW approach that extends the standard P-wave threshold based single station analysis to the whole network. The proposed method allows the real-time estimation of the potential damage at stations that are triggered by P-waves, as well as at the not-triggered ones, giving the advantage of a greater lead-time for the release of alerts. Results of tests made with synthetic data mimicking the scenario of the great 1755 Lisbon Earthquake, and those obtained by applying the new approach to available recordings, indicate that an EEW estimation of the potential damage associated with an event in the San Vicente Cape area can be obtained for a very large portion of the Iberian Peninsula

Mecanismos focales de terremotos en España

En este trabajo se presenta una recopilación de mecanismos focales de terremotos ocurridos en España entre 1950 y 1999 con focos superficiales (h <40 km) y magnitudes entre 4.0 y 8.3. También se han estudiado sismos de profundidad intermedia (40 <h < 150 km) y muy profunda (h 650 km) con magnitudes entre 3.5 y 7.0 ocurridos en el mismo periodo. Los resultados obtenidos para sismos superficiales indican predominio de movimientos de fallas inversas en el Golfo de Cádiz, normales y de desgarre en las Béticas y mar de Alborán. En la zona del Pirineo predominan los movimientos de fallas inversas con componentes de desgarre al igual que en la zona costero catalana. Los mecanismos de terremotos de profundidad intermedia indican en su mayoría movimientos verticales con eje de tensión vertical, mientras que en los terremotos muy profundos el eje de presión esta buzando unos 450 hacia el este. Estos resultados indican en superficie un régimen de esfuerzos horizontales compresivos en dirección N-S a NNW-SSE, con extensión horizontal en el mar de Alborán, consecuencia de la colisión entre Eurasia y Africa. La sismicidad a profundidad intermedia puede explicarse en términos de una subducción de material litosférico en el mar de Alborán sin conexión con la sismicidad muy profunda que sería debida a cambios súbitos de fase en el material

From strike-slip to reverse reactivation: The Crevillente Fault System and seismicity in the Bullas-Mula area (Betic Cordillera, SE Spain)

Several major N80ºE faults occur in the Bullas-Mula area (SE Spain). These faults and the numerous thrust slices of the Sierra de Ricote can be related to the movements of the Crevillente (or Cadiz-Alicante) fault system, which causes the westward displacement of the Betic Internal Zone and part of the External Zone. These faults moved with dextral strike-slip from Late Burdigalian to Early Tortonian. From this time on, the s1 position changed from a WNW-ESE direction to approximately N-S, giving rise to movements with a new reverse character. The focal mechanisms of the 1999 Mula earthquakes indicate a N80ºE nodal plane, and their pressure axes also coincide with the s1 direction existing from the Late Miocene and deduced from mesotectonic analysis at many points of the region. There is also good coincidence between their epicentral position and the fault traces. The Bullas earthquakes that occurred in 2002 are not directly related to the Crevillente faults, although their stress-pressure axes coincide with the s1 direction reported there

From strike-slip to reverse reactivation: The Crevillente Fault System and seismicity in the Bullas-Mula area (Betic Cordillera, SE Spain)

Several major N80ºE faults occur in the Bullas-Mula area (SE Spain). These faults and the numerous thrust slices of the Sierra de Ricote can be related to the movements of the Crevillente (or Cadiz-Alicante) fault system, which causes the westward displacement of the Betic Internal Zone and part of the External Zone. These faults moved with dextral strike-slip from Late Burdigalian to Early Tortonian. From this time on, the s1 position changed from a WNW-ESE direction to approximately N-S, giving rise to movements with a new reverse character. The focal mechanisms of the 1999 Mula earthquakes indicate a N80ºE nodal plane, and their pressure axes also coincide with the s1 direction existing from the Late Miocene and deduced from mesotectonic analysis at many points of the region. There is also good coincidence between their epicentral position and the fault traces. The Bullas earthquakes that occurred in 2002 are not directly related to the Crevillente faults, although their stress-pressure axes coincide with the s1 direction reported there

From strike-slip to reverse reactivation: The Crevillente Fault System and seismicity in the Bullas-Mula area (Betic Cordillera, SE Spain)

Several major N80ºE faults occur in the Bullas-Mula area (SE Spain). These faults and the numerous thrust slices of the Sierra de Ricote can be related to the movements of the Crevillente (or Cadiz-Alicante) fault system, which causes the westward displacement of the Betic Internal Zone and part of the External Zone. These faults moved with dextral strike-slip from Late Burdigalian to Early Tortonian. From this time on, the s1 position changed from a WNW-ESE direction to approximately N-S, giving rise to movements with a new reverse character. The focal mechanisms of the 1999 Mula earthquakes indicate a N80ºE nodal plane, and their pressure axes also coincide with the s1 direction existing from the Late Miocene and deduced from mesotectonic analysis at many points of the region. There is also good coincidence between their epicentral position and the fault traces. The Bullas earthquakes that occurred in 2002 are not directly related to the Crevillente faults, although their stress-pressure axes coincide with the s1 direction reported there