An earthquake yesterday morning off the Big Island's southeast coast rattled residents as far away as Maui and O'ahu, and was followed by a second noticeable quake in what a top volcanologist called an "unusual" spate of activity.

Authorities received no reports of damage or injuries, and the earthquakes did not generate tsunamis.

But yesterday morning's magnitude 5.2 earthquake, near the undersea seamount Lo'ihi, came just two days after a 5.2 quake was recorded 49 miles north of Hilo. Both were the largest earthquakes recorded in Hawai'i in six years.

Horst Sollfrank, who lives in Hawaiian Ocean View Estates near South Point on the Big Island, said he was working at his computer when the quake hit at 9:15 a.m. yesterday.

"The ground was shaking; I'm glad I was sitting down," he said. "Must have been pretty strong, I mean, I could feel the earth moving."

Big Island residents later felt a second quake at 4:32 p.m., also near Lo'ihi. It was first reported as one of magnitude 4.6, but later revised to 3.9.

"The last few days could be the first time we have had three earthquakes with magnitudes greater than 4.5 so widely scattered across the island," said Jim Kauahikaua, a geophysicist and scientist-in-charge at the U.S. Geological Survey's Hawaiian Volcano Observatory, speaking before the afternoon quake was revised to magnitude 3.9. "We are monitoring the situation."

Kauahikaua said it was too early to tell if the quakes are related, if they are random, or a portent of things to come.

"It could be a pattern that hasn't played out yet," he said. "This is way too early to tell. It certainly is unusual."

In all, the volcano observatory recorded five earthquakes of magnitude 3.1 or higher as of yesterday afternoon.

The first quake, an underwater event centered 69 miles south-southwest of Hilo, was felt on the Big Island, Maui and O'ahu.

Stan Toguchi, a 63-year-old salesman who lives behind Kaimuki High School, said he was reading the newspaper when the earthquake hit.

"I was sitting on my couch reading the newspaper and my couch started sliding sideways," Toguchi said. "I used to live in L.A., and I felt the rolling tremors before — up there was more scary. But you could really feel this one, it was scary."

Helene Berman, a 91-year-old Mo'ili'ili resident, said that when her couch began to shake, she thought her mind had finally failed her.

"It started up slowly, and got a little worse, then a little worse, then it calmed down," said Berman. "Maybe I'm sensitive to it (earthquakes). Born and raised in Kona, we always had earthquakes."

The second "felt" quake of the day happened at 4:32 p.m. on land, about two miles to the northeast of the morning earthquake.

Leighton Ah Cook, state Civil Defense duty officer, said no injuries or damage were immediately reported.

Yesterday morning's quake was the fifth earthquake recorded in Hawai'i with a magnitude of 5 or greater since January 2000.

Before Friday's quake, the last magnitude 5 earthquake was at 12:06 a.m. May 13, and was centered offshore near the Lo'ihi seamount, about 27 miles from Na'alehu.

Kauahikaua said it is not known what caused the quake, and added it is "very unlikely" that yesterday morning's quake is related to Friday's event. He said it is difficult to determine what is causing the quakes because the volcano observatory's sensors are on land, while any of the quakes' epicenters are offshore and underwater.

"This is the ninth time we've had more than one earthquake larger than magnitude 4.5 occur within the same week since our modern network was established in 1962. Some of those times were directly related to either large earthquakes or eruptions. Other times the earthquake groups were not directly related to anything," he said. "In each of those occurrences, the earthquake group was in the same area of the island."