Earthquakes
Expelled materials were visible on the north slope of the volcano, located some 270 kilometers (167 miles) northwest of San José in the province of Guanacaste.
Residents of the nearby community of Upala reported hearing a loud sound during the explosion, similar to that of a jet turbine. Mud and other materials from the volcano also fell on the Penjamo River and changed the water color, OVSICORI report stated.
The epicenter of Wednesday's tremor was located 9.5 kilometers southeast of Chiayi City Hall, at a depth of 18.3 kilometers, according to the CWB. Earlier in the day, a magnitude 4.1 temblor also shook the area.
USGS data

The city of Ukiah, in Northern California sits right next to the Maacama Fault, which is capable of M=7.5 earthquakes and poses a significant threat to the region.
The Maacama and Bartlett Spring faults lie approximately 50 km and 80 km east of the San Andreas respectively. All of these faults are members of the greater transform boundary between the Pacific and North American plates, a margin primarily composed of nearly pure right-lateral strike-slip faults. Both the Maacama and Bartlett Springs faults are known to be active based on seismicity and creep. Creep implies there is very slow, relatively continuous motion on a fault due to tectonic deformation. While faults that creep tend to not rupture in large earthquakes, the Hayward Fault running through the San Francisco East Bay creeps and has ruptured in M=7+ quakes. So, it is not a black and white rule.

This view from Bainbridge Island towards Seattle looks out across Puget Sound. The active Seattle Fault Zone runs through this area and poses a significant threat to the region.
The city of Seattle sits right on top of the Seattle Fault zone, an east-west-striking system of reverse faults within the Puget Lowland. While active, the Seattle Fault Zone is largely concealed as it lies at the southern end of the Seattle Basin, which is covered by surface deposits, water and dense vegetation. Nonetheless, by using LiDAR (light detection and ranging) the faults can be clearly seen (See image below). This complex system of reverse faults formed due to regional compression on the order of 0.5 cm/yr.

A map from the Pacific Northwest Seismic Network shows where the earthquake swarm is centered.
How long the shaking will continue is anyone's guess.
"Sometimes these swarms last years, sometimes they're over in an hour," Pacific Northwest Seismic Network Director John Vidale said Thursday.
The chances of a significant earthquake still remain low.
"The overwhelming odds are there is nothing damaging in our near future," Vidale said.
Though disconcerting to some residents, seismologists hope the ongoing earthquake swarm, centered between East Bremerton and Bainbridge Island, will reveal new information about the orientation of fault lines running beneath central Puget Sound.
The quakes have already offered some intriguing clues. Their depth for example — some 15 miles below the earth's surface — is below the level where the Seattle Fault is believed to lie, suggesting the activity could originate from another source.
"We just don't know," Vidale said, adding more research is needed to draw firm conclusions. "We're still figuring out what details we can decipher."
No reports of damages or tsunami warnings have been released.
Mexico is part of the so-called Pacific Ring of Fire, the most seismically active region of the Earth, where almost 90 percent of the world's earthquakes and volcanic eruptions occur.
The United States Geological Survey says a 2.2 magnitude earthquake hit around 9:50pm on Saturday.
It was reportedly centred about 5 km below the surface near the intersection of Wheatley Rd. and Essex Rd. 8.
Siobhan Cence says it sounded like a sonic boom shook the house, and it freaked her out a little.
"We heard a loud boom and felt the house shake just once really hard and I was shocked and thought was that me or did I feel something? My husband then looked at me and asked did you feel that and I said yeah," says Cence.
Cence says she can't ever remember an earthquake in Wheatley.
Cence says her husband quickly jumped into action because the bang was so loud.
The U.S. Geological Survey said the earthquake was recorded at a magnitude of 5.6 and occurred about 41 miles south southeast of Inarajan village, Guam. USGS initially recorded it at 5.5.
The earthquake had an undersea depth of 40 miles.
Inarajan Mayor Doris Lujan said she has not received initial reports of damage or injury.
Taiwan also recorded a 5.3 quake over the past 24 hours.

Volcanic activity on Campi Flegrei. The supervolcano has shown signs of unrest since the 1950s.
Campi Flegrei is a huge volcanic field that sits about 9 miles to the west of Naples, a city home to over a million people. It is made up of 24 craters and edifices, and appears as a large depression on the surface of the land.
The volcano last erupted in 1538 after almost a century of pressure building up. But though it lasted over a week, this was a comparably small one—40,000 years ago, it produced a "super-colossal" eruption. This is the second highest measure on the volcanic explosivity index, the first being "mega-colossal," like those seen at the Yellowstone supervolcano in the U.S. thousands of years ago.











Comment: Small earthquake shakes Seattle area days after swarm near Kitsap Peninsula