earthquake kills 260 dolphins in Peru

A family of bottlenose dolphins were enjoying a midnight snack on a school of anchovies when a 6.3 magnitude earthquake erupted near shore sending potent seismic pressure waves into the water, seriously injuring the dolphins and rupturing the swim bladders of the fish they we feasting upon!

(SeaQuake Solution Explains Centuries-Old Mystery of Whale Strandings—Link)

By 11 February 2012, at least 264 dead bottlenose dolphins had washed ashore along a 66 km stretch of sandy beach on Peru's northern coast. Vast quantities of dead anchovies were also found in the region. Bottlenose dolphins commonly reside near shore along the central and southern Peruvian Coast.

During this quake, both the dolphins, and the fish they were consuming, were exposed to powerful vertical shocks that entered the water near the coast. The sudden changes in ambient water pressure induced deadly barosinusitis in the dolphins and ruptured the swim bladders of the fish.

The dolphins were coastal water species and did not live-strand in a tight group as seen in offshore toothed whales. The dolphin species that resides near shore are familiar with shallow water and able to avoid beaching until near death.

The injury animals stayed near coast, and swam north with the surface currents for 7-8 days. They traveled ~500 miles downstream, arriving at the beaching site on 8 February. A strong shoreward wind kicked-up (watch the breaking waves in the background of this video) and washed the weak and dying dolphins ashore. They succumb to their injuries shortly after reaching the beach. The floating fish were also carried into the area by the surface currents.

Schools of dead fish floating on the surface after an undersea disturbance is not an uncommon phenomena. Nor should the idea that dolphins might be killed by an earthquake epicentered near shore come as a surprise especially considering a 1969 article in the Mariner's Weather Log (Vol. 11 (5) pp 161-164) entitled "Seaquakes: Shakers of Ships." Therein, Lt. Frank Rossi reported:

"Although the epicenter was located 30 miles inland, the large shallow-focused Mexican earthquake of 3 June 1932 was felt by many vessels at sea. The S/S Solana, steaming through a smooth sea with light variable winds in water over 4,800 feet deep, 60 miles from the epicenter, experienced strong violent shaking for about seven seconds. Only 10 miles away, the M/V Sevenor experienced less severe vibrations but lasting nearly a minute. Conditions aboard the M/V Northern Sun were entirely different. Although the vessel was 115 miles from the epicenter, vibrations lasting for three minutes became so violent that the engines were stopped. Before the earthquake, the sea was smooth with a slight westerly swell, but after the event the sea had become confused and the swell pattern had changed. Further to the North, 130 miles from the epicenter, the S/S Arizona commenced to vibrate and continued to do so for about 75 seconds. The aftershocks continued for many days. Ship reports indicated that during the next 36 hours several strong seaquakes were experienced in the area. The M/V Silerwillow began to vibrate dangerously in every part and at the same time began an uneven short pitching motion followed by heavy rolling. The disturbances commenced at 0530 GMT on 4 June, and the rolling continued 15 minutes. Seven hours later at 1245 GMT the crew aboard the S/S Talmanca heard a loud noise like distant gunfire, then experienced severe vibrations, and at 1337 GMT two similar gunfire reports were heard again about 10 seconds apart but there were no apparent vibrations. However, 20 minutes later the sea surface was littered for five or six miles with small dead fish. Several hours later, the S/S Hanover reported violent shocks that "rocked the ship as a nearby explosion might." Fifteen minutes later two more shocks were felt."

Although the Deafwhale Society has noticed that many baleen whales have washed ashore after earthquakes along the California Coast, this is the first time in our 40 years of research that we have tied an earthquake near the shoreline to a mass killing of coastal water dolphins.

There was one mass killing reported in June 1946 in which an undersea earthquake near Vancouver Island was thought responsible for the death of five gray whales. (link)

Earthquakes on shore are known to generate powerful hydroacoustic pressure waves in the water. For example, in 2003, an earthquake onshore near the coast of New Zealand generated a series of LF pressure waves that enter the water, traveled 1,800 miles across the Tasman Sea, and struck the coast of Sidney, Australia, with such a force that residents rushed outside of their houses thinking a local earthquake had occurred.(link)

Normally, an earthquake on land would not injury dolphins in the water unless the event was close to the shore. USGS, AZUR, GFZ, and CPP located this event about 30 km from the beach; however, the Harvard Seismic Station (HARV) located the epicenter at the shoreline. My opinion is the Harvard group is closer to correct based on the lack of total destruction in the town of Ica. I think Ica would have been flattened had this town been directly above the focal point.