Strong Earthquakes Shakes Remote Far-Western China on November 25, 2016
6.9-Magnitude Earthquake Strikes Off the Coast of Japan and Triggers Tsunami Alarms (November 22, 2016)
A 6.9-magnitude earthquake has been reported in Fukushima, Japan, by the United States Geological Survey (USGS). Fukushima’s Iwaki City shore is detecting a tsunami now, according to Japan Broadcasting Corporation (NHK), which is currently broadcasting a live shot from the city’s Onahama port. A 2-foot-high tsunami was observed at the post at 6:49 a.m. local time (ABC News)
Tsunamis are long-wavelength, long-period sea waves produced by the sudden or abrupt movement of large volumes of water. Large waves produced by an earthquake, a submarine landslide, an underwater explosion, or a meteorite impact can overrun nearby coastal areas in a matter of minutes. Not all earthquakes produced tsunamis. Actually thrust fault (also known as reverse fault) and normal fault earthquakes can cause large tsunamis because these earthquakes can uplift or down-drop the sea floor.
Tsunamis have an extremely long wavelength up to several hundred kilometers long. The period is also very long, about an hour in deep water. In the deep sea, a tsunamis height can be only about 1 m tall; it is not felt aboard a ship or seen from air in open ocean (but can be measured by buoy or satellite altimeter). Tsunamis are often barely visible when they are in the deep sea. This makes tsunami detection in the deep sea very difficult. Here we are dealing with shallow waters. (Imode)
Oklahoma Residents Hit by Induced Earthquakes Sue Energy Companies (November 18, 2016)
Residents of a town hit by Oklahoma’s strongest earthquake have filed a class-action lawsuit against dozens of energy companies, accusing them of triggering destructive temblors by injecting wastewater from oil and natural gas production underground. Pawnee residents filed the suit Thursday in district court against 27 companies, saying they operate wastewater injection wells even though they know the method causes earthquakes. The lawsuit seeks an unspecified amount for property damage and reduced value, plus emotional distress. A magnitude 5.8 earthquake struck the town of about 2,200 in September and the lawsuit claims 52 more have hit the area since. On Nov. 6, a magnitude 5.0 quake damaged dozens of buildings in nearby Cushing, a town that is home to one of the world’s largest oil hubs. Oklahoma has had thousands of earthquakes in recent years, with nearly all traced to underground wastewater disposal. Some scientists say that the high-pressure injection of massive amounts of chemical-laced wastewater deep in the earth induces the quakes. Regulators have asked oil and gas producers to either close injection wells or reduce the volume of fluids they inject. (abcnews.go.com)
Earth provides us energy resources (e.g., oil, gas, coal, and geothermal) that we need to better our lives. Yet Earth can also kill us even more frequently these days; earthquakes and volcanic eruptions are the major sources. Moreover, the earth’s reaction to energy production can also produce earthquakes which can shake us severely and can damage property. The earthquakes associated with energy production belong to a broad category of earthquakes known as induced (human-caused) earthquakes. Sources of induced earthquakes include the injection of large amounts of fluid in the subsurface and the withdrawal of large amounts of fluid from the subsurface. Other potential sources of induced earthquakes include the injection of municipal and industrial wastes into the earth.
Recently, several seismic events have been felt and reported by local residents in the United States in areas where natural tectonic seismic activity is uncommon and where shale-gas development and production are ongoing. So far, none of these events have resulted in loss of life or significant structural damage. Yet they have raised public attention and concern about the potential link between these events and shale-gas development and production. To add perspective to this issue, we describe in Tables below the recent earthquake history in three states of the United States with large shale-gas development and production projects—namely, Texas, Oklahoma, and Ohio.
In all these regions we can notice a sudden large increase in the number of earthquakes in the last 14 years compared to similar previous periods of time, especially in Texas and Oklahoma. Most of these earthquakes have a magnitude smaller than 5. We can use the spatial and temporal proximity of the earthquakes and shale-gas development and production in these tables to infer a correlation between these earthquakes and shale-gas development and production. Basically, we are dealing here with previously aseismic regions which are now experiencing a larger rate of occurrence of multiple earthquakes compared to their historical rates. The shale-gas development and production projects in these regions may probably be caused by tectonic changes. However, the results in these tables do not represent scientific proof of a correlation between earthquakes in these regions and shale-gas development and production projects. Moreover, the variations in the occurrence of multiple earthquakes suggest that even if such correlations may exists, they will depend on the local tectonic conditions. More importantly, we do not know yet the potential long-term effects of large increases in the rate of these occurrences (Imodeeducation.com and imodeedupack.com).
2016 Central Italy Earthquakes (August-November, 2016)
An earthquake, measuring 6.2 on the moment-magnitude scale, hit Central Italy on 24 August 2016 at 3:36 AM local time (01:36 UTC). Its epicenter was Norcia closed to Accumoli, with its focus (hypocenter) at a depth of 4 km (USGS and Istituto Nazionale di Geofisica e Vulcanologia). This earthquake was followed by at least 2500 aftershocks which were felt across the whole of central Italy, including Naples, Rome, Florence, and Bologna. About 300 people were killed. This was the largest tremor since 2009, when an earthquake in the Abruzzo region killed more 300 people. The same day at 4:33 AM local time, a moment-magnitude 5.5 earthquake struck the same region and at the same depth of 10 km. About 8 hours later (1:50 PM local time ), another moment-magnitude 4.9 earthquake struck Visso.
Two other earthquakes of moment magnitudes 5.4 and 5.9 (about two hours apart) occur in the same region on 26 October 2016. A third larger earthquake measuring 6.5 on the moment-magnitude scale, struck the same region on 30 October at 7:40 AM local time.
There is a large network of fractures and faults of various sizes which cross the earth’s crust. This network is central to the occurrence of potential natural and induced earthquakes. Under the right conditions, any of these faults or a network of fractures can lead to earthquakes through slippage.
Can we map or image this network?
What is the connectivity of the elements of this network in terms of tectonic stresses?
The answers to these questions will very likely bring us closer to the short-term prediction of the earthquake.
Also, what are the possibilities that one or more failures of this network can trigger a chain reaction of near simultaneous earthquakes?