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Did You Feel It 50 Years Ago? the 1969 m7.9 Cape Saint Vincent Earthquake

Description: 

On February 28^th 1969 a major earthquake took place offshore SW Iberia, on the diffuse boundary between the Eurasian and African plates. The earthquake was widely felt in Iberia and Morocco, with maximum intensities of VIII recorded in SW Portugal. With an estimated magnitude Ms 7.9, this event is currently the highest magnitude felt earthquake in the European historical catalog. The earthquake was recorded in Portugal by one WWSSN seismic station in Oporto and another two stations in Lisbon and Coimbra, but all records were saturated. One strong-motion accelerometer located in the pier of a recently built bridge over the Tagus river provided the closest non-clipped record of the earthquake.

Whereas source parameters for this major earthquake were studied mostly from teleseismic records, information on the ground motion was mostly obtained from macroseismic observations. In 2019, on the occasion of the 50^th anniversary of the 1969 earthquake, we revisited this topic by launching a Did You Feel It (DYFI) inquiry about the 1969 earthquake. This initiative occurred at a time when many testimonies of the 1969 earthquake are still alive and have a clear – often even vivid – memory of the earthquake.

In this presentation we will discuss the key aspects of our study, namely: limitations of the DYFI questionnaire made 50 years after the earthquake; new information revealed by the DYFI; comparison between our DYFI intensities and the traditional macroseismic intensities; comparison between the intensities / ground motion pattern revealed by the DYFI and that observed in recent moderate magnitude (M5-6) earthquakes; intensities pattern revealed in the capital city of Lisbon.

Session: Tectonics and Seismicity of Stable Continental Interiors

Type: Oral

Date: 4/19/2023

Presentation Time: 11:00 AM (local time)

Presenting Author: Susana Custodio

Student Presenter: No

Invited Presentation: 

Authors