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originally posted by: JWill
Arrival of the P wave before the S wave.
There are accounts of "artillery"-like sounds that were said to have occurred before or during the New Madrid earthquakes of 1811-1812.
That must be a little tense.
Loud, booming noises have startled people across the United States, and it was unclear what was actually happening or if the separate events were even related. Residents in Alabama, California, Idaho, Michigan and New Jersey reported hearing similar mysterious sounds. Most recently, the noises were heard in Colorado, CBS Denver reports. The Monday sounds left CBS Denver’s meteorologist Chris Spears baffled. The only possible conclusion he could offer was that meteors from the Leonid meteor shower were bursting in the sky, creating the loud noises. Ron Hranac, an astronomy expert, struck down that theory, saying that the meteors produced by the Leonids were way too small for that to happen, according to CBS Denver.
Mammoth Mountain, a lava-dome complex, lies on the southwest topographic rim of Long Valley Caldera. The 3,369-m (11,053 ft) high volcano lies west of the structural rim of the caldera and is considered to represent a magmatic system distinct from Long Valley Caldera and the Mono-Inyo Craters. Eruptions at Mammoth Mountain occurred from 100,000 ot 50,000 years ago. Mammoth Mountain is surrounded by at least 35 mafic vents that are part of the same magmatic system and include Red Cones, two closely spaced basaltic cinder cones located southwest of Mammoth Mountain and southeast of Devils Postpile National Monument. The cones, whose name derives from colorful mantling scoria deposits, are unglaciated and were radiocarbon dated at about 8,000 years ago. Phreatic eruptions, distinct from those at South Inyo Craters, took place about 700 years ago from vents on the north side of Mammoth Mountain. Recent volcanic unrest, including seismicity, gas emission, and tree kill, is thought to be related to a dike intrusion beneath Mammoth Mountain in 1989. Both Long Valley Caldera and Mammoth Mountain have experienced episodes of heightened unrest over the last few decades (earthquakes, ground uplift, and/or volcanic gas emissions). As a result, the USGS manages a dense array of field sensors providing the real-time data needed to track unrest and assess hazards.
originally posted by: eManym
Here is an explanation. Its the sound of the US Army blowing up old munition at the Hawthorne Army Depot in western Nevada. They claim the noise is bouncing off the atmosphere causing the booms to be heard on the other side of the Sierras.
Mysterious 'Boom' Explained