July 29, 2013 – 1,270 Peruvian Earthquakes 1973 to 2012: I downloaded 1,270 earthquakes from the USGS for Peru, greater than or equal to 5.0 magnitude, and graphed them by local time of day (see above). I wanted to compare yesterday’s study, with Japanese earthquakes, but using a larger database.
I was particularly interested in Peru, since the country does not have daylight savings time and only one time zone. Therefore, I was able to make an accurate chart of the time for 1,270 quakes. Below, is a hazards map of Peru, from the USGS. As you can see, the greatest danger is along the “Ring of Fire” just of the west coast of the country.
As in yesterday’s study of Japan, my goal was to analyze statements made by Pliny the Elder or Gaius Plinius Secundus (23-79AD); a Roman officer and author of the Natural History Encyclopedia, published in 78AD. Specifically, Pliny states that earthquakes are: “(1) More frequent by night than in the daytime, (2) Severest in the morning and evening and (3) Are frequent near dawn and in the daytime about Noon.” Pliny is apparently separating frequency (quantity) and severity (strength).
‘(1) Pliny: “More frequent by night than in the daytime.”
I assuming nighttime is the 12 hour period from 6PM to 5AM totaling 609 quakes. Daytime is the 12 hours between 6AM to 5PM totaling 661. Using these definitions, day and night both have 12 hours. Therefore, at least for Japan Pliny is wrong; in that 48% of the quakes occurred at night, while 52% happened in the day time.
‘(2) Pliny: “Severest in the morning and evening.”
Morning: The period of time between midnight and noon, especially from sunrise to noon. Evening: The period of time at the end of the day, usually from about 6PM to bedtime. I’m going to modify these Google definitions as follows: Morning = Six hours from 6AM to 11AM = 327 quakes, Evening = Six hours from 6PM to 11PM = 336 quakes. This means the morning AND the evening total is 663 (52.2%), while the other 12 hours equals 607 (47.8%). The quantity is greatest in the other 12 hour category. Pliny gets a no on this one.
‘(3) Pliny: “Are frequent near dawn and in the daytime about noon.”
Dawn = 4AM to 6AM = 131 quakes (average 44 per hour). Noon = 11AM to 1PM = 152 quakes (average 51 per hour). The Chart average per hour = 53. Both dawn and noon are below the average for the entire sample. Pliny (pictured below) doesn’t get a win on this one.
Summary: Score Pliny 1 win and 2 loses. A recent study, using Japanese quakes, had Pliny the Elder with 1 win, 1 lose and 1 tie. Perhaps things have changed since 78 A.D. since the ancient Roman scholars earthquake pronouncements. One thing I have noticed in both studies is an exponential trend line that slope up left to right, meaning that as the day progresses from midnight, earthquakes tend to increase.
The Master of Disaster