An earthquake struck Western Greece near the coastal city of Aigio at on 15 June 1995. The second destructive earthquake to strike Greece in a month, it measured 6.4–6.5 on the moment magnitude scale (). It was assigned a maximum Modified Mercalli intensity of VIII (Severe) and EMS-98 intensity of IX (Destructive). The horizontal peak ground acceleration reached 0.54 g and ground velocity peaked at —the strongest ground motion ever recorded in Greece. Fifteen minutes after the mainshock, a large aftershock struck, causing further damage to Aigio. Faulting occurred on either the Aigion fault or an unnamed offshore fault. Other faults in the region have the potential to produce earthquakes up to 6.9, which poses a risk to Aigio and the surrounding Gulf of Corinth.
Monetary damages from the earthquake reached $660 million (in 1995 USD). Significant destruction occurred; the collapse of two buildings left 26 dead and up to 200 injured. In the aftermath, several countries and organizations provided disaster aid, including search and rescue and refugee assistance operations. Many countries also donated medical supplies, temporary shelter, water treatment equipment, and a ship to house survivors. The Greek government issued seismic loans to aid in the rebuilding of Aigio, though it may have encouraged the construction of taller buildings—increasing Aigio's future seismic hazard. Controversy arose over the lack of a warning for the earthquake, as several sources warned officials that a major earthquake would occur.
Tectonic setting
Western Greece is affected by the ongoing back-arc extension within the Aegean Sea Plate caused by the subduction of the African Plate in the Hellenic subduction zone. Stresses in the region create normal faults to accommodate the /yr extensional strain. In the Gulf of Corinth, faults have formed as a result of these stresses to accommodate some of the fastest known rates of continental extension. Crustal normal faults do not extend further than deep in this region, as at that depth the crust transitions to mantle at the Mohorovičić discontinuity.
The Aigion fault is a north-dipping, west-northwest trending (fault direction), young (at most 300,000 years old) fault that has been growing in the past couple of hundred thousand years through the linking of several fault segments. The fault is composed of two main segments: an offshore and an onshore portion, and they extend for combined. The fault is also wide. It started developing at earliest 300,000 years ago, and its slip has increased over time. The onshore Aigion fault has a slip rate between /yr and /yr at a dip angle of 50 to 60 degrees with a strike of 100 degrees; the offshore segment slips at /yr at a dip angle of 60 degrees. It has a throw of and a dip of 55 degrees to the north. The Aigion fault reactivated during this earthquake. It showed surface rupturing and produced the largest aftershock. The Aigion fault influences the physical malforming of fan-deltas and associated alluvial plains, thus controlling the geomorphology of a by area.
There are two other major faults near Aigio. The Eliki fault, which runs near the town of Eliki, and the Psathopyrgos fault, which is near the village of Psathopyrgos. The Eliki fault initially developed between 0.7 and 1 million years ago. The fault is split into two segments: the West Eliki and East Eliki faults. The West Eliki fault is long, and has a dip of 60 degrees; the East Eliki fault runs for . The Psathopyrgos fault is a major fault structure lying at the western end of the Gulf of Corinth. The fault is long, deep, has a dip of 60 degrees, and a strike of 87 degrees.
Geology
Before the earthquake struck, strange phenomena were reported in the region. Minutes before the 6.4–6.5 earthquake struck, people from several areas near the epicenter claimed to have heard the sound of a strong wind in otherwise calm weather. There were also multiple reports of strange animal activity such as dogs running away, and cats being frightened. Earthquake lights were also reported before the shock within a radius of the epicenter. A "bright red glow" was reported shortly before the earthquake struck. Fifteen minutes after the mainshock, the largest aftershock ( 5.6) struck and had a maximum Modified Mercalli intensity (MMI) of VI. Thousands of aftershocks were recorded daily while temporary seismometers were stationed in the vicinity of the epicenter.