Articles | Volume 16, issue 8
Nat. Hazards Earth Syst. Sci., 16, 1967–1977, 2016
Nat. Hazards Earth Syst. Sci., 16, 1967–1977, 2016

Research article 22 Aug 2016

Research article | 22 Aug 2016

New study on the 1941 Gloria Fault earthquake and tsunami

Maria Ana Baptista1,2, Jorge Miguel Miranda2,3, Josep Batlló4, Filipe Lisboa3, Joaquim Luis2,5, and Ramon Maciá6 Maria Ana Baptista et al.
  • 1Instituto Superior de Engenharia de Lisboa, Instituto Politécnico de Lisboa, Lisbon, Portugal
  • 2Instituto Dom Luiz, Universidade de Lisboa, Lisbon, Portugal
  • 3Instituto Português do Mar e da Atmosfera, Lisbon, Portugal
  • 4Institut Cartográfic i Geològic de Catalunya, Barcelona, Spain
  • 5Universidade do Algarve, Faro, Portugal
  • 6Dept. de Matemàtiques, Universitat Politècnica de Catalunya, Barcelona, Spain

Abstract. The M ∼ 8.3–8.4 25 November 1941 was one of the largest submarine strike-slip earthquakes ever recorded in the Northeast (NE) Atlantic basin. This event occurred along the Eurasia–Nubia plate boundary between the Azores and the Strait of Gibraltar. After the earthquake, the tide stations in the NE Atlantic recorded a small tsunami with maximum amplitudes of 40 cm peak to through in the Azores and Madeira islands. In this study, we present a re-evaluation of the earthquake epicentre location using seismological data not included in previous studies. We invert the tsunami travel times to obtain a preliminary tsunami source location using the backward ray tracing (BRT) technique. We invert the tsunami waveforms to infer the initial sea surface displacement using empirical Green's functions, without prior assumptions about the geometry of the source. The results of the BRT simulation locate the tsunami source quite close to the new epicentre. This fact suggests that the co-seismic deformation of the earthquake induced the tsunami. The waveform inversion of tsunami data favours the conclusion that the earthquake ruptured an approximately 160 km segment of the plate boundary, in the eastern section of the Gloria Fault between −20.249 and −18.630° E. The results presented here contribute to the evaluation of tsunami hazard in the Northeast Atlantic basin.

Short summary
This is a new study on the 25 November 1941 earthquake and tsunami, Northeast Atlantic. The tsunami was recorded from Morocco to the UK. We present a new epicentre location and use tsunami data to compute the tsunami source. Results show that the earthquake ruptured a segment of the Eurasia–Nubia plate boundary. Other segments of the plate boundary may rupture and generate similar events. These conclusions are important for tsunami hazard assessment in the Northeast Atlantic.
Final-revised paper