An ageing chihuahua who vanished after the 6.6 magnitude Grassmere earthquake has returned home nine days after going missing.

Owner Allen Coleman said he was not expecting to see 12-year-old Echo alive again before he found him sitting at the front door on Sunday afternoon.

Neither he nor his daughter, Dawn Coleman, have any idea where Echo has been or how he survived.

"After the third day I thought we would be looking for a body," Mr Coleman said. "I did not think we would see him again."

Ms Coleman said whatever Echo was doing, "that was his story".

"It's a mystery with a happy ending. It was such a surprise. Everybody thought I was joking."

Echo had been sitting on the front porch of their Seddon farm when the quake hit but the family was pre-occupied with a boar that had taken off down the road, she said.

Of their seven dogs, including Echo's daughter Lucky, he was the last one they expected to wander off, she said.

"He maybe had a knock and thought, ‘I'm getting out of here'."

Mr Coleman guessed Echo was hit by something that had fallen during the earthquake which had frightened him.

Echo might not have been far away because he suddenly showed up after Mr Coleman's granddaughters visited for the first time since the jolt.

"He loves them," he said. "They were with the horses and talking pretty loud. Maybe that triggered him to come out of his hiding place."

Echo was thirsty and hungry when he showed up on Sunday, he said.

Ms Coleman said he had lost a lot of weight.

"But he got a big welcome from all the other dogs, they were sniffing round him," she said.

"We had another aftershock last night [Sunday] and he took off again but he didn't go far."