Archive for the ‘Uncategorized’ Category

Magnitude 7.2 – 37km NE of Pinotepa de Don Luis, Mexico – February 16, 2018

February 17, 2018

USGS Event Page
Magnitude 7.2 – 37km NE of Pinotepa de Don Luis, Mexico
2018-02-16 23:39:42 UTC
16.646°N   -97.653°W
24.7 km depth
USGS – Seismotectonics of Mexico

“Located atop three of the large tectonic plates, Mexico is one of the world’s most seismically active regions. The relative motion of these crustal plates causes frequent earthquakes and occasional volcanic eruptions. Most of the Mexican landmass is on the westward moving North American plate. The Pacific Ocean floor south of Mexico is being carried northeastward by the underlying Cocos plate. Because oceanic crust is relatively dense, when the Pacific Ocean floor encounters the lighter continental crust of the Mexican landmass, the ocean floor is subducted beneath the North American plate creating the deep Middle American trench along Mexico’s southern coast. Also as a result of this convergence, the westward moving Mexico landmass is slowed and crumpled creating the mountain ranges of southern Mexico and earthquakes near Mexico’s southern coast. As the oceanic crust is pulled downward, it melts; the molten material is then forced upward through weaknesses in the overlying continental crust. This process has created a region of volcanoes across south-central Mexico known as the Cordillera Neovolcánica.
The area west of the Gulf of California, including Mexico’s Baja California Peninsula, is moving northwestward with the Pacific plate at about 50 mm per year. Here, the Pacific and North American plates grind past each other creating strike-slip faulting, the southern extension of California’s San Andreas fault. In the past, this relative plate motion pulled Baja California away from the coast forming the Gulf of California and is the cause of earthquakes in the Gulf of California region today.
Mexico has a long history of destructive earthquakes and volcanic eruptions. In September 1985, a magnitude 8.0 earthquake killed more than 9,500 people in Mexico City. In southern Mexico, Volcán de Colima and El Chichón erupted in 2005 and 1982, respectively. Paricutín volcano, west of Mexico City, began venting smoke in a cornfield in 1943; a decade later this new volcano had grown to a height of 424 meters. Popocatépetl and Ixtaccíhuatl volcanos (“smoking mountain” and “white lady”, respectively), southeast of Mexico City, occasionally vent gas that can be clearly seen from the City, a reminder that volcanic activity is ongoing. In 1994 and 2000 Popocatépetl renewed its activity forcing the evacuation of nearby towns, causing seismologists and government officials to be concerned about the effect a large-scale eruption might have on the heavily populated region. Popocatépetl volcano last erupted in 2010.”


Magnitude 2.7 – SE of East Kingston, New Hampshire – February 15, 2018

February 15, 2018

Exeter, NH, Amesbury, MA, and Newburyport, MA had the highest number of “Did You Feel It?” online responses!

If you felt it, please fill out a USGS Felt Report here:

USGS: Earthquakes in New England
“People in New England, and in its geological extension southward through Long Island, have felt small earthquakes and suffered damage from infrequent larger ones since colonial times. Moderately damaging earthquakes strike somewhere in the region every few decades, and smaller earthquakes are felt roughly twice a year. The Boston area was damaged three times within 28 years in the middle 1700’s, and New York City was damaged in 1737 and 1884. The largest known New England earthquakes occurred in 1638 (magnitude 6.5) in Vermont or New Hampshire, and in 1755 (magnitude 5.8) offshore from Cape Ann northeast of Boston. The Cape Ann earthquake caused severe damage to the Boston waterfront. The most recent New England earthquake to cause moderate damage occurred in 1940 (magnitude 5.6) in central New Hampshire.Earthquakes in the central and eastern U.S., although less frequent than in the western U.S., are typically felt over a much broader region. East of the Rockies, an earthquake can be felt over an area as much as ten times larger than a similar magnitude earthquake on the west coast. A magnitude 4.0 eastern U.S. earthquake typically can be felt at many places as far as 100 km (60 mi) from where it occurred, and it infrequently causes damage near its source. A magnitude 5.5 eastern U.S. earthquake usually can be felt as far as 500 km (300 mi) from where it occurred, and sometimes causes damage as far away as 40 km (25 mi).Faults
Earthquakes everywhere occur on faults within bedrock, usually miles deep, although some New England earthquakes occur at shallower depths. Most of New England’s and Long Island’s bedrock was assembled as continents collided to form a supercontinent 500-300 million years ago, raising the northern Appalachian Mountains. The rest of the bedrock formed when the supercontinent rifted apart 200 million years ago to form what are now the northeastern U.S., the Atlantic Ocean, and Europe.At well-studied plate boundaries like the San Andreas fault system in California, often scientists can determine the name of the specific fault that is responsible for an earthquake. In contrast, east of the Rocky Mountains this is rarely the case. New England and Long Island are far from the nearest plate boundaries, which are in the center of the Atlantic Ocean and in the Caribbean Sea. New England is laced with known faults but numerous smaller or deeply buried faults remain undetected. Even the known faults are poorly located at the depths of most earthquakes. Accordingly, few, if any, earthquakes in New England can be linked to named faults. It is difficult to determine if a known fault is still active and could slip and cause an earthquake. As in most other areas east of the Rockies, the best guide to earthquake hazards in New England and Long Island is the earthquakes themselves.”  –USGS

Magnitude 7.9 – 280km SE of Kodiak, Alaska – January 23, 2018

January 23, 2018

USGS Event Page
M 7.9 – 280km SE of Kodiak, Alaska
2018-01-23 09:31:42 UTC
56.046°N   -149.073°W
25.0 km depth

Seismotectonics of Alaska
USGS “The Aleutian arc extends approximately 3,000 km from the Gulf of Alaska in the east to the Kamchatka Peninsula in the west. It marks the region where the Pacific plate subducts into the mantle beneath the North America plate. This subduction is responsible for the generation of the Aleutian Islands and the deep offshore Aleutian Trench.” To read more on the tectonics of Alaska, click here.