The 10 km (6.2 mi) deep mainshock, which measured 6.1 on the moment magnitude scale caused significant damage on Faial Island.

[3] The largest recorded earthquake in the vicinity of the Azores was the 1941 magnitude 8.3 event which was associated with strike-slip faulting on the Eurasian–Nubian plate boundary.

[4] The Azores Islands are situated atop a triple junction zone where the North American, Eurasian and African plates meet.

[7] Two zones of faulting occur around the 1998 earthquake epicenter; WNW–ESE and NNW–SSE trending systems with steep dip angles to the NNE or SSW and WSW or ENE, respectively.

South of the volcanic caldera and on the western part of Faial Island, similar-striking faults also occur.

[5] The earthquake was assigned a maximum Mercalli intensity of VIII in the northeastern corner of Faial Island, where the greatest destruction was observed.

[9] A large number of schools on both islands were moderately damaged; the most affected was a kindergarten in Salão, where its external masonry walls collapsed, leading to the demolition of the entire structure.

Concerned about aftershocks, residents of Faial and Pico islands slept inside tents provided by the government.

[12] The Portuguese Air Force deployed a Lockheed C-130 Hercules plane carrying tents and thousand blankets from Lisbon; medical teams and supplies also arrived.

In response, the Office of Foreign Disaster Assistance aided US$20,000 to the U.S. embassy for the Portuguese government to purchase lavatory items and distribute them to the affected communities.