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'If there were a remote tsunami in Japan or off the coast of Chile, it would be two to three hours or longer before it would impact the San Diego coast," says senior emergency services coordinator Susan Asturias. "The Alaska Tsunami Warning Center will call it off eventually, but typically, when they issue these warnings, they're not able to confirm whether [a tsunami] is going to happen or not." On Saturday, July 29, the National Weather Service in San Diego will host a tsunami workshop at which representatives from the State Office of Emergency Services, San Diego County Office of Emergency Services, and the National Weather Service will discuss the threat of tsunamis and how to prepare for them.

"The largest tsunami we've had here was three feet...but that doesn't mean [a larger one] can't happen; we're always fighting complacency," says Asturias.

A tsunami is a series of fast-traveling waves caused by earthquakes or landslides on the ocean floor. "People who live in or frequent coastal areas need to know that if they feel shaking when they're on the beach, that's the first clue for a local tsunami and they should head inland or go as high up as soon as possible."

According to the Office of Emergency Service's website, the largest tsunami on record for Southern California was in 1960, when waves four and a half feet tall struck the coasts of Santa Monica and Port Hueneme, causing major damage to harbors in Los Angeles and Long Beach.

Tsunami waves can travel up to 600 miles per hour and are likely to carry debris. The first wave is rarely the largest, and some of the last may arrive hours after the first wave hits.

For surfers and swimmers, there can be other dangers lurking about. From July 30 to August 5, the Birch Aquarium at Scripps will celebrate Shark Week with a series of shark-related activities including shark expert Dr. Jeffrey Graham's presentation "Southern California Sharks."

There are nearly a dozen species of shark living off the San Diego coast. "Sharks real close to the surf zone are smooth-hound and leopard sharks," says Graham. "In the kelp beds there are horn, swell, angel, and soup-fin sharks. Further offshore -- within a mile or two of the shoreline -- are blue sharks, mako sharks, and thresher sharks. Sevengill cow sharks [which live in deeper water and can grow to be ten feet long] are famous for eating dogs," he adds. "They have interesting behaviors; they team up, get a squad together, and go after seals. A young seal and a dog might look alike to them."

Cow sharks may be rare in Southern California, but their seal-eating cousins, the great whites, are, according to Graham, "likely to occur close to shore in La Jolla, where harbor seals come out of the water."

For the presentation, Graham will introduce two graduate students who will discuss their current research. One, Nick Wegner, is researching the movement patterns of mako sharks.

"Makos are considered the fastest-swimming fish in the ocean -- fastest of the sharks and maybe fastest of all fish," says Wegner. "We've clocked a mako moving at 14.8 meters per second, which translates to 33 miles per hour." Makos are open-ocean fish that eat smaller fish like mackerel. Similar to threshers, makos can grow to over 1000 pounds. "A more typical shark, such as the blue shark, has reportedly reached burst speeds of about 25 miles per hour." The average swimming speed for most sharks, including mako and blue sharks, is between .60 and 1.55 miles per hour.

Wegner's fellow graduate student, Dan Cartamil, will speak about the thresher shark. "The thresher's tail is as long as the rest of their entire body," says Cartamil. "The typical shark we'll see is two or three hundred pounds, but there are monsters out there that get up to a thousand pounds. Despite the fact they get this huge, they feed on small fish, like anchovies or sardines. [Threshers] herd the fish into a little ball with their giant tail, and then they whack the ball of fish with their tail and stun them." Cartamil explains that threshers are the only fish to be caught by the tail, rather than the mouth, on an angler's hook. "They whack the hook with their tail." -- Barbarella

Tsunami Workshop Saturday, July 29 9:30 a.m. to 12:30 p.m. Town and Country Convention Center 500 Hotel Circle North Mission Valley Cost: Free (limited space; RSVP to edwin.clark@noaa.gov ) Info: 858-565-3490 or www.sdcounty.ca.gov/oes/

Southern California Sharks Monday, July 31 6:30 p.m. to 8 p.m. Birch Aquarium at Scripps 2300 Expedition Way La Jolla Cost: $8 (reservations required; call 858-534-4109) Info: 858-534-3474 or http://aquarium.ucsd.edu

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