Man Made Earthquakes Have Been Happening in Texas Since the 1920s

Earthquakes triggered by human activity have been happening in Texas since at least 1925, and they have been widespread throughout the state ever since, according to a new historical review of the evidence published online May 18 in Seismological Research Letters.

The earthquakes are caused by oil and gas operations, but the specific production techniques behind these quakes have differed over the decades, according to Cliff Frohlich, the study's lead author and senior research scientist and associate director at the Institute for Geophysics at the University of Texas at Austin.

Frohlich said the evidence presented in the SRL paper should lay to rest the idea that there is no substantial proof for human-caused earthquakes in Texas, as some state officials have claimed as recently as 2015.

At the same time, Frohlich said, the study doesn't single out any one or two industry practices that could be managed or avoided to stop these kinds of earthquakes from occurring. "I think we were all looking for what I call the silver bullet, supposing we can find out what kinds of practices were causing the induced earthquakes, to advise companies or regulators," he notes. "But that silver bullet isn't here."

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How to Detect Earthquakes (Venusquakes?) on Venus From Orbit

Detecting an "earthquake" on Venus would seem to be an impossible task. The planet's surface is a hostile zone of crushing pressure and scorching temperatures--about 874 degrees F, hot enough to melt lead--that would destroy any of the normal instruments used to gauge seismic activity. But conditions in Venus' atmosphere are much more hospitable, and it is here that researchers hope to deploy an array of balloons or satellites that could detect Venusian seismic activity--using sound.

These kinds of low frequency or infrasonic sound waves, much lower than an audible voice, are already measured on Earth. The rumbling or "hum" can be generated by sources as diverse as volcanoes, earthquakes, ocean storms and meteor air blasts. In recent years, says Los Alamos National Laboratory researcher Stephen Arrowsmith, infrasonic observations have undergone a renaissance of sorts, especially as a relatively inexpensive way to monitor atmospheric nuclear weapons tests. But last year, a team of experts convened by the Keck Institute for Space Studies began thinking of ways to use infrasonic observations to get a better look at the geological dynamics of Venus.

At about 50-60 kilometers above Venus' surface, the temperature and pressure conditions are much more like those on Earth, albeit with a denser atmosphere. This dense atmosphere helps translate any seismic waves into infrasonic waves that can be detected with instruments floating above the planet's surface, says Jim Cutts, a Jet Propulsion Laboratory researcher who participated in the Keck conference. Infrasonic waves can be "felt" as either fluctuations in pressure, or as light emissions called airglow, or electron disruptions in Venus' upper atmosphere.

Arrowsmith and colleagues say that barometric pressure changes might be detected with a series of balloons in the Venus cloud layer at 55 kilometers above the surface, such as those launched by the Soviet Union in Venus' atmosphere in the 1980s. In a second talk, Philippe Lognonné and colleagues discuss a complementary way to analyze the planet's infrasonic waves, using orbiting satellites to detect airglow. In both cases, the first goal will be determine what the noise-to-signal ratio might be for these two techniques. The researchers want to know if the instruments onboard a balloon or satellite will be sensitive enough to detect and identify a seismic signal in the midst of other infrasonic waves, and how large of a seismic event might be detected by these observations.

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Massive Earthquake(s?) at the Triassic-Jurassic Extinction

Intense and widespread seismicity during the end-Triassic mass extinction due to emplacement of a large igneous province

Authors:

Lindström et al

Abstract:

Multiple levels of earthquake-induced soft-sediment deformations (seismites) are concentrated in the end-Triassic mass extinction interval across Europe. The repetitive nature of the seismites rules out an origin by an extraterrestrial impact. Instead, this intense seismic activity is linked to the formation of the Central Atlantic magmatic province (CAMP). By the earliest Jurassic the seismic activity had ceased, while extrusive volcanism still continued and biotic recovery was on its way. This suggests that magmatic intrusions into sedimentary strata during early stages of CAMP formation caused emission of gases (SO2, halocarbons, polycyclic aromatic hydrocarbons) that may have played a major part in the biotic crisis.

A-OK at Home

It shook a little, but no harm here.

Great Tsunamigenic Earthquakes in Alaska are More Common Than Previously Thought

Great tsunamigenic earthquakes during the past 1000 yr on the Alaska megathrust

Authors:

Shennan et al

Abstract:

Large to great earthquakes and related tsunamis generated on the Alaska megathrust produce major hazards for both the area of rupture and heavily populated coastlines around much of the Pacific Ocean. Recent modeling studies suggest that single-segment ruptures, as well as multi-segment, 1964-type ruptures, can produce great earthquakes, >M8, and significant hazards both in the near field and to distant locations through the generation of tsunamis. We present new paleoseismological data from Kodiak Island and a new analysis of radiocarbon data based on Bayesian age modeling to combine our observations with previous geological, historical, and archaeological investigations. We suggest that, in addition to multi-segment ruptures in A.D. 1964 and 1020–1150 (95% age estimate), a single-segment rupture occurred in 1788, with coseismic land-surface deformation across Kodiak Island and a tsunami that is recorded in historical documents and in sediment sequences, and another, similar rupture of the same Kodiak segment at A.D. 1440–1620. These indicate shorter intervals between ruptures of the Kodiak segment than previously assumed, and more frequent ruptures than for the Prince William Sound segment.