No, this is not a blog about the unintended consequences of two nuclear superpowers, sitting on the notorious “Ring of Fire” (above map), contemplating blasting each other with nukes… unleashing fault fractures and resulting quakes. And yes, I’ve thought about that too. “The Ring of Fire is a 25,000 mile (40,000 km) horseshoe-shaped area of intense volcanic and seismic (earthquake) activity that follows the edges of the Pacific Ocean. Receiving its fiery name from the 452 active and dormant volcanoes that lie within it, the Ring of Fire includes 75% of the world's active volcanoes and is also responsible for 90% of the world's earthquakes.” Thoughtco.com. Massive slabs of the earth’s crust sitting on an ocean of molten rock, constantly shifting, moving, opening escape holes (volcanos) for unbelievable pressures from below.
I live on that Ring of Fire (Los Angeles) and have been through a number of shakers, one (the 6.7 Richter Scale Northridge quake in 1994; 57 deaths, $20 billion in damage) that seriously damaged my house such that I had to move out for six months to allow repairs. But these were nothing compared to the tumblers that slammed into Mexico in the last few weeks: A nasty 8.1 off-shore quake that decimated the Chiapas area (southern part of Mexico) on September 7th (almost one hundred fatalities; a 6.1 aftershock hit in nearby Oaxaca on September 23rd felt in Mexico City), and a 7.1 9/19 shaker that hit south of Mexico City (the fourth most populous city on earth – 23.4 million), 32 years to the day from the September 19, 1985 8.1 quake (just to the west of Mexico City) that killed 9,500, injured 30,000, demolishing 3,000 buildings in the Mexican capital and seriously damaging 100,000 additional structures.
The numbers for the most recent (9/19/17) quake near Mexico City continue to mount, heading towards 300+ deaths, but just looking at the collapsed buildings – the shaker hit mid-day when those buildings were full – I suspect that the casualties will wind up being much higher. Still, one of the big questions these earthquakes raised for me is how to understand exactly how nature’s catastrophic disasters are measured. We’ve faced massive hurricanes and earthquakes of late.
For example, if a hurricane is a narrow band of nasty – versus the wide Irma killer that stretched across the entire state of Florida – or lingers over one area for a longer period (like Harvey that literally sat over Houston without budging) – how relevant are the 1 through 5 categories we always hear to describe them? Scientists are moving away from the “Cat” measurements into a 50 point scale (Hurricane Severity Index) that take these variables into consideration.
Likewise, the science of measuring and understanding earthquakes has moving on from the measurement system devised in the 1930s by Charles Richter. Duration, the overall size, the type of material that comprises the affected area and how deep the quake is (deeper quakes do less damage than comparable surface temblors) of a relevant quake impact its intensity. Richter does not measure those variables. The Richter Scale is exponential: “For each whole-number increase in magnitude, the seismic energy released increases by about 32 times. That means a magnitude 7 earthquake produces 32 times more energy — or is 32 times stronger — than a magnitude 6… A magnitude 8 releases 1,000 times more energy than a magnitude 6, but it releases that energy over a larger area and for a longer time…” Rong-Gong Lin II writing for the Los Angeles Times, September 22nd.
So since the 1990s we have moved on to other “magnitude” measures. Like the Modified Mercalli Intensity scale. Rong-Gong continues: “The moment magnitude scale measures the movement of rock along the fault, and accurately measures larger earthquakes, which can last for minutes and affect a much larger area; the Richter scale did not accurately record such quakes… The U.S. Geological Survey has a calculator that can help you make these calculations. So, for instance, a magnitude 8.2 — probably the strongest earthquake that could hit Southern California on the San Andreas fault — would produce an astonishing 178 times more energy than the magnitude 6.7 Northridge earthquake in 1994…
“Magnitude is important, but a key factor is where a quake strikes. The ones most people care about strike under or near heavily populated areas… Generally, earthquakes of magnitude 6 and above are the ones for concern. When nearby, they can cause shaking intensities that can begin to break chimneys and cause considerable damage to the most seismically vulnerable structures, such as non-retrofitted brick buildings… Earthquakes of magnitude 7 and above can overturn heavy furniture and inflict considerable damage in ordinary buildings.
“If you were in Northridge [California, 1994], right on top of where the earthquake fault moved, you faced what’s known as intensity 9 shaking, defined by the Modified Mercalli Intensity scale as ‘violent’ — enough to shift a structure off its foundation.... Here’s the USGS’ explanation [of that scale; italics addedblog]:
Intensity 10: Extreme — Some well-built wooden structures destroyed; most masonry and frame structures destroyed with foundations. Rails bent.
Intensity 9: Violent — Damage considerable in specially designed structures; well-designed frame structures thrown out of plumb. Damage great in substantial buildings, with partial collapse. Buildings shifted off foundations.
Intensity 8: Severe — Damage slight in specially designed structures; considerable damage in ordinary substantial buildings with partial collapse. Damage great in poorly built structures. Fall of chimneys, factory stacks, columns, monuments, walls. Heavy furniture overturned.
Intensity 7: Very strong — Damage negligible in buildings of good design and construction; slight to moderate in well-built ordinary structures; considerable damage in poorly built or badly designed structures; some chimneys broken.
Intensity 6: Strong — Felt by all, many frightened. Some heavy furniture moved; a few instances of fallen plaster. Damage slight.
Intensity 5: Moderate — Felt by nearly everyone; many awakened. Some dishes, windows broken. Unstable objects overturned. Pendulum clocks may stop.
Intensity 4: Light — Felt indoors by many, outdoors by few during the day. At night, some awakened. Dishes, windows, doors disturbed; walls make cracking sound. Sensation like heavy truck striking building. Standing motor cars rocked noticeably.
Intensity 3: Weak — Felt quite noticeably by persons indoors, especially on upper floors of buildings. Many people do not recognize it as an earthquake. Standing motor cars may rock slightly. Vibrations similar to the passing of a truck. Duration estimated.
Intensity 2: Weak — Felt only by a few persons at rest, especially on upper floors of buildings.
Intensity 1: Not felt — Not felt except by a very few under especially favorable conditions.”
There’s no index for suffering, for the deep psychological scars of trauma, the loss of hope, rebuilding a life – sometimes without a loved one who perished in the debacle – a home or a livelihood, but these pains endure. Understanding how we measure physical impacts of nature’s wrath… a step in understanding the rest that requires more empathy than the desensitizing litany of global disasters instills in the minds of too many of us. Natural disasters reflect individual stories of loss, pain and suffering… multiplied by numbers that should scare all of us.
I’m Peter Dekom, and the biggest casualties across the globe seem to be a dramatic plunge in understanding and empathy.
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