Monday, December 26, 2016

Is A New Age Of Pressure Upon Us? - 12

Fig. 1
(Most active quake zones: Japan, Black Sea)
Based on about 50,000 earthquake records in my SQL database, two areas stand out, in terms of number of earthquakes  (outlined in red in Fig. 1) where faults exist.

The area around Japan (between latitude 30-50N, longitude 130-150E) is the top quake-count area with 16,547 quakes having taken place in that area between 1772 and 2013.

Fig. 2 Quakes per year

The annual distribution of those quakes over the years is shown in Fig. 2.

The totals for the three individual WOD zones in the Japan area are: Zone 1313 had 11,081 quakes; Zone 1314 had 2,435 quakes; and Zone 1414 had 3,031 quakes.

Fig. 3
The area with the second-most number of quakes is located near the Black Sea (between latitude 30-50N, longitude 40-50E).

Fig. 4  Black Sea area sea level change
Total quake-count for the two zones was 4,904 quakes having taken place in that area between 1785 and 2012.

Of that, Zone 1304 had 2,537 quakes and Zone 1404 had 2,367 quakes.

The yearly distribution of those quakes in those zones is shown in Fig. 3.

Fig. 5 Japan area sea level change
I discussed the Black Sea area in a previous post or two.

That was back when I was using a different zone map, and when I was focusing on the anomalously high sea level rise there (The Ghost-Water Constant - 5, Zone AJ, Quadrant SE, Sub-quadrant NW).

Fig. 6 Ocean Temperatures
Additionally, the context in those posts did not include earthquakes as the current series on "pressures put on the Earth's crust" does.

Those posts also focused in on a more narrow geographical area than the current post does.

Fig. 7 Ocean Temperatures
A very high sea level rise has taken place in that smaller area, about a half a foot higher than the area we are focusing on today.

Thus, the sea level rise graph at Fig. 4 does not show as intense of an amount of sea level rise as the more narrow focus did (about 4.1 ft. compared to about 3.6 ft.).

Even more strange in a sense, the sea level rise in the Japan area, where the most quakes took place, experienced even less sea level rise (Fig. 5).

This observation does show that there is no direct relation between the number of earthquakes and the amount of sea level rise in a given geographical area.

But it does show that as sea level changes increase over time, it can impact the number of quakes even if not in a mathematically exact way.

As it turns out, we can say that sea level rise and fall can change the degree of pressure being put on the Earth's crust, and further, that those changing pressures can trigger quakes in hair-trigger areas.

The same can be said for quakes taking place away from oceans and coastlines:
The number of earthquakes has increased dramatically over the past few years within the central and eastern United States. Nearly 450 earthquakes magnitude 3.0 and larger occurred in the four years from 2010-2013, over 100 per year on average, compared with an average rate of 20 earthquakes per year observed from 1970-2000.

This increase in earthquakes prompts two important questions: Are they natural, or man-made? And what should be done in the future as we address the causes and consequences of these events to reduce associated risks? USGS scientists have been analyzing the changes in the rate of earthquakes as well as the likely causes, and they have some answers.

USGS scientists have found that at some locations the increase in seismicity coincides with the injection of wastewater in deep disposal wells. Much of this wastewater is a byproduct of oil and gas production and is routinely disposed of by injection into wells specifically designed for this purpose.
...
Although it may seem like science fiction, man-made earthquakes have been a reality for decades. It has long been understood that earthquakes can be induced by impoundment of water in reservoirs, surface and underground mining, withdrawal of fluids and gas from the subsurface, and injection of fluids into underground formations.
(USGS, "Man-Made Earthquakes Update"; cf. this). Some forms of changing the volume and mass of water in an area is known, but not well understood:
The column of water in a large and deep artificial lake alters in-situ stress along an existing fault or fracture. In these reservoirs, the weight of the water column can significantly change the stress on an underlying fault or fracture by increasing the total stress through direct loading, or decreasing the effective stress through the increased pore water pressure. This significant change in stress can lead to sudden movement along the fault or fracture, resulting in an earthquake. Reservoir-induced seismic events can be relatively large compared to other forms of induced seismicity. Though understanding of reservoir-induced seismic activity is very limited, it has been noted that seismicity appears to occur on dams with heights larger than 330 feet (100 m). The extra water pressure created by large reservoirs is the most accepted explanation for the seismic activity. When the reservoirs are filled or drained, induced seismicity can occur immediately or with a small time lag.
(Wikipedia, "Seismicity"). The key is whether or not an earthquake fault line is being affected, which is more likely in the far-and-wide reaching reality of all of the world's oceans being changed in terms of depth, mass, and volume (1 m3 of water weighs 2,204.623 lbs. --about 1 compact car).

But seismic science is not fine-tuned enough to say exactly where quakes will take place as a result of sea level change.

No, it is at this time only a general observation about general eventualities, which are clear (see graphs in this series).

In the future this might improve to become as accurate as one scientist who predicted a specific volcano would erupt as the ice melted in the cryosphere of Iceland (Is A New Age Of Pressure Upon Us? - 4).

In closing, I added the water temperature records from the World Ocean Database (WOD) as shown in Fig. 6 and Fig. 7.

Those two graphs are added just to reiterate that ocean water temperature is not a major factor in sea level change, as has been discussed at length on Dredd Blog (On Thermal Expansion & Thermal Contraction, 2, 3, 4, 5, 6, 7, 8, 9).

The previous post in this series is here.

Steppin' In A Slide Zone ...



No comments:

Post a Comment