USGS Shakemap - 1993 Scotts Mills earthquake

The 1993 Scotts Mills earthquake, also known as the "Spring break quake", occurred in the

U.S. state In the United States, a state is a constituent political entity, of which there are 50. Bound together in a political union, each state holds governmental jurisdiction over a separate and defined geographic territory where it shares its sover ...

Oregon Oregon () is a U.S. state, state in the Pacific Northwest region of the Western United States. The Columbia River delineates much of Oregon's northern boundary with Washington (state), Washington, while the Snake River delineates much of it ...

on March 25 at 5:34 AM

Pacific Standard Time The Pacific Time Zone (PT) is a time zone encompassing parts of western Canada, the western United States, and western Mexico. Places in this zone observe standard time by subtracting eight hours from Coordinated Universal Time (UTC−08:00). ...

. With a

moment magnitude The moment magnitude scale (MMS; denoted explicitly with or Mw, and generally implied with use of a single M for magnitude) is a measure of an earthquake's magnitude ("size" or strength) based on its seismic moment. It was defined in a 1979 pape ...

of 5.6 and a maximum perceived intensity of VII (''Very strong'') on the

Mercalli intensity scale The Modified Mercalli intensity scale (MM, MMI, or MCS), developed from Giuseppe Mercalli's Mercalli intensity scale of 1902, is a seismic intensity scale used for measuring the intensity of shaking produced by an earthquake. It measures the eff ...

, it was the largest earthquake in the

Pacific Northwest The Pacific Northwest (sometimes Cascadia, or simply abbreviated as PNW) is a geographic region in western North America bounded by its coastal waters of the Pacific Ocean to the west and, loosely, by the Rocky Mountains to the east. Though ...

since the Elk Lake and Goat Rocks earthquakes of 1981.

Ground motion Ground motion is the movement of the earth's surface from earthquakes or explosions. Ground motion is produced by seismic waves that are generated by sudden slip on a fault or sudden pressure at the explosive source and travel through the earth a ...

was widely felt in Oregon's

Willamette Valley The Willamette Valley ( ) is a long valley in Oregon, in the Pacific Northwest region of the United States. The Willamette River flows the entire length of the valley and is surrounded by mountains on three sides: the Cascade Range to the east, ...

, the

Portland metropolitan area The Portland metropolitan area is a metro area in the U.S. states of Oregon and Washington centered on the principal city of Portland, Oregon. The U.S. Office of Management and Budget (OMB) identifies it as the Portland–Vancouver–Hillsboro, ...

, and as far north as the

Puget Sound Puget Sound ( ) is a sound of the Pacific Northwest, an inlet of the Pacific Ocean, and part of the Salish Sea. It is located along the northwestern coast of the U.S. state of Washington. It is a complex estuarine system of interconnected ma ...

area near

Seattle Seattle ( ) is a seaport city on the West Coast of the United States. It is the seat of King County, Washington. With a 2020 population of 737,015, it is the largest city in both the state of Washington and the Pacific Northwest regio ...

Washington Washington commonly refers to: * Washington (state), United States * Washington, D.C., the capital of the United States ** A metonym for the federal government of the United States ** Washington metropolitan area, the metropolitan area centered o ...

Earthquake

The Scotts Mills mainshock

epicenter The epicenter, epicentre () or epicentrum in seismology is the point on the Earth's surface directly above a hypocenter or focus, the point where an earthquake or an underground explosion originates. Surface damage Before the instrumental pe ...

was located about east of the town of Scotts Mills in Marion County, and about south of

Portland Portland most commonly refers to: * Portland, Oregon, the largest city in the state of Oregon, in the Pacific Northwest region of the United States * Portland, Maine, the largest city in the state of Maine, in the New England region of the northeas ...

. The

United States Geological Survey The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, ...

reported that strong motion instruments recorded

peak ground acceleration Peak ground acceleration (PGA) is equal to the maximum ground acceleration that occurred during earthquake shaking at a location. PGA is equal to the amplitude of the largest absolute acceleration recorded on an wikt:accelerogram, accelerogram at a ...

s of 0.06 g at

Detroit Dam Detroit Dam is a gravity dam on the North Santiam River between Linn County and Marion County, Oregon. It is located in the Cascades, about west of the city of Detroit. It was constructed between 1949 and 1953 by the United States Army Corps o ...

, to the southeast, and also give an extensive review of damage reports and ground motion intensities. Reports of the earthquake came from as far as Roseburg in southern Oregon, south of the epicenter, to the coastal town of Lincoln City, east to Bend, and north to Seattle. The seismology lab from the

University of Washington The University of Washington (UW, simply Washington, or informally U-Dub) is a public research university in Seattle, Washington. Founded in 1861, Washington is one of the oldest universities on the West Coast; it was established in Seattle a ...

in Seattle reported the Richter magnitude to be 5.4, but stated that the initial figure could change. An aftershock measuring 3.2 happened within the first hour of the main shock.

Damage

Most structural damage consisted of toppled chimneys and failure of walls of unreinforced

masonry Masonry is the building of structures from individual units, which are often laid in and bound together by mortar; the term ''masonry'' can also refer to the units themselves. The common materials of masonry construction are bricks, building ...

. Buildings with damage include Molalla High School, the

State Capitol This is a list of state and territorial capitols in the United States, the building or complex of buildings from which the government of each U.S. state, the District of Columbia and the organized territories of the United States, exercise its ...

in Salem, and the St. Paul Church in

Saint Paul Paul; grc, Παῦλος, translit=Paulos; cop, ⲡⲁⲩⲗⲟⲥ; hbo, פאולוס השליח (previously called Saul of Tarsus;; ar, بولس الطرسوسي; grc, Σαῦλος Ταρσεύς, Saũlos Tarseús; tr, Tarsuslu Pavlus; ...

. The damage at the capitol occurred in the old wing and that section of the facility was closed after the morning earthquake, and two walls at the high school were partially collapsed. Additional damage to some homes occurred in Molalla in the form of broken windows and brick planters at some homes there. No damage was reported in Portland, but residents did see books knocked off shelves and some car alarms were set off. Several people were treated at the Salem Hospital for injuries related to falling glass.

Previous events

A similar sized earthquake occurred in 1877 and Portland was struck by a magnitude 5.5 quake in 1962, but geophysicists say the area is vulnerable to even larger earthquakes, such as the

1872 North Cascades earthquake The 1872 North Cascades earthquake occurred at in central Washington Territory (now Washington state). A maximum Mercalli intensity of VIII (''Severe'') was assessed for several locations, though less intense shaking was observed at many other ...

References

External links

Increased seismic activity in Oregon highlighted by tremor and a M=4.0 quake
– Temblor, Inc. * {{DEFAULTSORT:Scotts Mills Earthquake, 1993 1993 in Oregon 1993 in Washington (state) 1993 earthquakes Clackamas County, Oregon

1993 File:1993 Events Collage.png, From left, clockwise: The Oslo I Accord is signed in an attempt to resolve the Israeli–Palestinian conflict; The Russian White House is shelled during the 1993 Russian constitutional crisis; Czechoslovakia is peace ...

Marion County, Oregon 1993 natural disasters in the United States

Earthquake

Damage

Previous events

See also

References

External links