The 7.0 Mw Neftegorsk earthquake shook the former Russian settlement of Neftegorsk with a maximum Mercalli intensity of IX (Violent). Total damage was $64.1-300 million, with 1,989 deaths and 750 injured. The settlement was not rebuilt.
The 1995 Neftegorsk earthquake occurred on 28 May at 1:04 local time on northern Sakhalin Island in the Russian Far East. It was the most destructive earthquake known within the current territory of Russia, with a magnitude of Ms7.1 and maximum Mercalli intensity of IX (Violent) that devastated the oil town of Neftegorsk, where 1,989 of its 3,977 citizens were killed, and another 750 injured.90% of the victims were killed by the collapse of 17 five-story residential buildings. While Western media generally attributed the collapses to allegedly poor construction and shoddy materials of Soviet-era construction, a geotechnical study faulted a failure to accommodate the possibility of soil liquefaction in an area that was considered "practically aseismic".The Belgian Centre for Research on the Epidemiology of Disasters' EM-DAT database places the total damage at $64.1 million, while the United States' National Geophysical Data Center assesses the damage at $300 million.This quake was not only catastrophic, it was totally unexpected: earthquakes with magnitudes greater than 6 were not known to occur in the area of northern Sakhalin Island. It is also of great scientific interest (some 20 papers have been published) because it occurred near a poorly known tectonic plate boundary where the Okhotsk Plate (connected with North American Plate) is crashing into the Amurian Plate (part of the Eurasian Plate), and indicates that the plate boundary is associated with a north–south striking seismic belt that runs the length of Sakhalin. More precisely, this earthquake occurred on the Upper Piltoun fault (also known as the Gyrgylan'i—Ossoy fault), which branches off the main Sakhalin-Hokkaido fault that runs along the east side of the island.35 km (22 mi) of surface rupturing was observed (46 km including a branching fault), with an estimated average lateral displacement of about 4 meters, but up to 8 m (9 yd) in some places. (This compares to 14 km of slip estimated to have accumulated on the Sakhalin-Hokkaido fault in the last 4 million years.) The unusual strength of this quake and length of rupturing, and the low level of seismic activity beforehand, has been attributed to the accumulation of strain over a long period of time on a locked fault segment.