Bali, Indonesia ? Sirens blared and thousands of people fled the coast Tuesday as Indonesia held its largest-ever tsunami drill. Others across Asia prayed at mass graves, chimed temple bells and lit candles two years after devastating waves claimed 230,000 lives.

There was a jarring reminder of the continued threat in the seismically charged region when a powerful earthquake struck off southwestern Taiwan, prompting a brief alert that a damaging tsunami might be headed toward the Philippines. No big waves materialized.

Sharon Howard, whose fiance and two children were among those killed in the Dec. 26, 2004, tsunami, one of the worst natural disasters in living memory, was one of dozens of survivors to return to white sand beaches to honor lost love ones.

“I miss them. They were my life,” the British tourist said, tears pouring down her cheeks after attending a memorial ceremony on Khao Lak beach in Thailand. “I wish I could turn back time and they could all come back.”

The most powerful earthquake in 40 years ruptured the sea floor off Indonesia’s westernmost island, Sumatra, displacing billions of tons of water and sending towering walls of water roaring across the Indian Ocean at jetliner speeds into fishing villages, luxury resorts and bustling coastal towns.

Some 167,000 of the deaths were on Sumatra’s northern tip, with Sri Lanka, India and Thailand accounting for most of the rest.

Some mourners observed a moment of silence at the exact time the waves crashed ashore, while others lit incense on the beach, offered prayers and threw flowers into the sea. Thai authorities also opened a cemetery for hundreds of unidentified tsunami victims.

But along with the commemorations another push was under way, with governments, volunteers and residents taking steps to protect against future tsunamis.

Those efforts gained urgency when Tuesday’s earthquake brought a warning that yard-high waves could hit the east coast of the Philippines, but there were no known evacuations in the region, and no damage was reported.

In Sri Lanka, the first of 100 tsunami warning towers was erected on a beach. Volunteers in Malaysia replanted mangroves, which some say act as a natural barrier against killer waves.

Indonesia said its tsunami drill on Bali – a resort island unaffected by the 2004 disaster – was aimed at raising the public’s awareness of safety measures and testing technology deployed over the last two years.