San Francisco unlikely to be epicenter of big quake: Indian seismologist
Sep 4 : Last month's occurrence of 70 earthquakes in just 48 hours along the "Pacific Ring of Fire" sparked fears that a big temblor is on the way to rattle California on the US West Coast.
The Ring of Fire around the edge of the Pacific Ocean is a 40,000-km-long, horseshoe-shaped, seismically-active belt that passes through California. San Francisco in northern California, which suffered a massive earthquake in 1906, is reportedly on high alert.
But Arun Bapat, a Pune-based research seismologist and former chief of earthquake research at the Central Water and Power Research Station, who had predicted the 2004 Indian ocean tsunami, believes that San Francisco is unlikely to be hit.
"It is possible that California may be visited by a quake of magnitude more than 7, but I am not sure whether the epicenter could be at San Francisco," Bapat told this correspondent in an email.
"Based on my research, after having checked some parameters of the deadly 1906 San Francisco earthquake, I would say that the rupture during that earthquake was from San Juan to Telegraph Hills -- a distance of 270 miles (432 km)," Bapat said.
"The rupture travels from San Juan in the south to Telegraph Hills in the north. If the northern parts of San Francisco were ruptured about a century back, there could be still some remnants of the ruptured rocks. The south of San Juan is more virgin for rupture. This is the logic of my reasoning that the probable epicenter could be about 70- to 100-km south of San Francisco."
Bapat's confidence stems from the string of correct predictions he has made about impending earthquakes for years.
"I have been working in the fields of earthquake and allied sciences, including earthquake forecasting," Bapat explained.
The massive January 2001 earthquake in Bhuj was one such prediction he made when he heard about water suddenly oozing out of the ground and sprouting in the form of springs in some locations in Gujarat's Kutch district.
The strange event invited curious onlookers but it rang an alarm bell in Bapat who had read reports that sprouting of groundwater had preceded the Kangra earthquake (April 4, 1905) and the Quetta earthquake (May 30, 1935).
Without losing time, Bapat e-mailed the Gujarat government that the event witnessed in Kutch "is a sign of large-magnitude earthquake occurring within 2-3 weeks". His warning was ignored.
But his prediction came true on January 26 (India's Republic Day) when Bhuj was shaken by 7.9 magnitude quake -- hence known as the Republic Day quake -- that killed around 10,000 people.
"Seismic precursors such as water oozing from the ground, and abnormal animal behavior before a large magnitude earthquake cannot be quantified," Bapat reports in the journal Current Science. "But these are highly reliable and should be used by the authorities for mitigation measures."
Abnormal behavior of domestic animals like cows, buffaloes, dogs, cats, horses, lambs about 10 hours before earthquakes has been observed and reported before the Uttarkashi earthquake of 1991, Latur earthquake of 1993, Bhuj earthquake of 2001, Sumatran earthquake and tsunami of 2004, and the Kashmir earthquake of 2005, Bapat said.
The oldest record of abnormal animal behavior before an earthquake is available for the Kangra earthquake of 1905, when animals in the Lahore Zoo -- about 180 km from the epicenter -- reportedly became "noisy, violent, and aggressive".
The 6.5 magnitude earthquake that rocked China on August 8, 2017 killed 19 people and injured 247. Not many are aware that Bapat had warned his Chinese colleagues about its occurrence only a day before it struck.
Bapat alerted his Chinese counterpart after seeing a satellite infra-red image in the Indian Meteorological Department (IMD) website. It showed a "thermal high" in the China-Japan region that was not there five hours earlier -- which Bapat knew was a sign of a moderate to large magnitude earthquake within the next few hours.
That forecast turned to be correct as was his prediction of the 7.2-magnitude Mexico earthquake of April 18, 2014, two months before the actual event.
Bapat's predictions using satellite readings of some seismological and geophysical parameters like "Total Electron Content" and "Outgoing Long wave Radiation", in addition to infra-red images of the earth, had also turned out to be correct.
For instance, using these data, on 14 April, 2017, Bapat alerted the Chief Secretary of Jammu and Kashmir government of a possible earthquake of magnitude around 5.5 "within the next few days". An earthquake of magnitude 5.0 did occur four days later, 79-km from Kargil, as predicted.
This satellite-borne data could be effectively used for earthquake forecasting and prediction on a 24x7 basis, says Bapat. "The data is freely available on the Indian Meteorological Department website."
Besides satellite data, there are seismic precursors that Bapat has used for forecasting.
"About two days before an earthquake, the landline telephone communication gets disturbed; radio reception fades away about 30 to 40 hours before the event and television reception gets disturbed about 10 hours before an earthquake," Bapat said.
"About 100 minutes before the occurrence of a moderate to large magnitude earthquake, all mobile telephones stop functioning."
These precursors were noticed prior to the 1993 Latur earthquake in Maharashtra, the Bhuj quake of 2001 and the 7.5 magnitude Kathmandu quake on April 25, 2015.
Bapat's prediction based on surface temperature also turned out to be correct in the case of the earthquake in Manipur early last year.
(K.S. Jayaraman is a veteran science journalist. He can be contacted at firstname.lastname@example.org)