Like all those whose lives have been touched by catastrophe, Dubliner Pamela Dix has a deep sense of what it feels like for the relatives of those who are missing after the attacks on America. For eleven days, she had no news of her brother Peter, a passenger on Pan Am flight 103, which blew up in the air and then crashed at Lockerbie in Scotland 13 years ago.

After her brothers body was identified she went to see the disaster site on Christmas Day, just as the families of those involved in the Twin Towers attacks have been travelling to New York.

"You were grappling with an unreal event and going to the scene helped to try and make it real," she said. "It is almost impossible to accept that it has happened to you unless you see it, at the time I deliberately did not watch any of the television coverage I wanted to see it for myself. Visiting that place will be a significant experience for the bereaved it is the last place their relatives will have been."

People who have been exposed to such trauma in the past say they felt an appalling sense of deja vu as the tragedy unfolded in America. Scale is insignificant - whether it is five or five thousand lives, the loss of a loved one is the same. Two young boys are blown up in an IRA attack on Warrington, 270 people perish at Lockerbie, 31 lives are lost after a bomb explodes in the quiet market town of Omagh. Dunblane, Hillsborough, or Birmingham - the tragedies may be unique but the consequences are the same. Communities traumatised. Individuals bereft. Each left to cope with unspeakable grief when the television cameras eventually retreat.

In recent days, these people have found themselves reliving their own experiences and empathising with relatives and survivors in America.

Pamela Dix, who lives in Woking, Surrey, waited three hours on September 11th last to find out if another brother and his family, who are based in Manhattan, were safe.

A press officer for Disaster Action, a charity set up to support the bereaved after a series of disasters in Britain during the 1980s, she says people find their own ways of going forward. "Talking to others who were affected is very important," she said. "Other people who have been through it understand and can talk for hours about what happened."

The father of Aidan Gallagher, one of those who died in Omagh, said he found it difficult to get out of bed the morning after the attacks on America and that for many people in the community, the events of September 11th had a particularly bitter resonance.

On the Shankill Road this week, another community has been sharing the pain of those in the US. A memorial garden to the 45 victims of nine bomb attacks on the road over the past 30 years, including the 1993 bomb in a fish shop which killed nine people - has also become a place to remember victims of the attacks in the US.

Mina Wardle, the Director of the Shankill Road Stress and Trauma Centre which counsels relatives of victims, says some of her clients cannot bear to watch the pictures from America any more. She said they were listening to relatives of those who died in the attacks give interviews and saying, "God love them, they don't know what is going to come next," with the insight of people who have been there before.

"Whenever there is a shooting or a bomb victim or anything like this you relive your trauma all over again," she said. "I have really shed tears this week, tears for America and tears for what I have seen in my own community," she said.

Writer Don Mullan, author of books about Bloody Sunday and the Dublin/Monaghan bombings was in Pennsylvania when the attacks occurred, and visited the site of the third hijacked plane that crashed before reaching its probable target, the White House in Washington. He later travelled to New York, and visited Ground Zero.

"You could smell death," he said. The community spirit evident in Manhattan reminded him of another community's reaction: "I was thinking very much about how the people of Derry rallied around the families at the time of Bloody Sunday, there was a tremendous sense that people had come through a shared experience and this kind of support is everywhere in New York," he said.

Such events can reduce victims to mere statistics, according to Howard Davis, a senior lecturer in disasters and trauma with Lancashire University. Recalling the Piper Alpha disaster where 167 people died after an explosion on an oil rig, he referred to a comment one of the bereaved: "I am not a Piper Alpha widow, I am Jim's widow."

"The victims of extreme experiences can become lost as a people, and because of the visibility of something like what happened in New York it is impossible for those left behind to get away from it," he said.

A social worker during the time of the Hillsborough disaster in 1989, when 95 people died in a crush at a football stadium, Davis said blame or retribution-seeking is a natural reaction for those whose loved ones have died. He also warned that those of us with ordered lives, untouched by tragedy, can often pathologise relatives and survivors, viewing them as uncomfortable reminders of the events. We can therefore often miss the positive contributions and wisdom of people who have been through extreme experiences, he said.

Colin Parry lost his 12-year-old son Tim in 1993 when two bombs exploded in Warrington. Three-year-old Jonathan Ball was also killed in the attack. "Watching what is happening in America does bring back the sense of absolute helplessness and loss those people will be feeling you keep thinking you are a bystander in all of it, that you weren't there to help your loved one and it is an awful feeling," he said.

Parry believes the wider community and those directly involved in these events can react in one of three different ways: there are those who are inspired to do something, even though they don't know what; those who would rather pretend it never happened; and those who can talk about it but don't see the point in doing anything positive. The majority fall into the final category, he said.

For their part, the Parry family reacted by setting up a trust which saw the Tim Parry and Jonathan Ball Peace Centre open in March this year, the seventh anniversary of the attack. The centre, which has a 40-bed residential wing, is dedicated to conflict resolution and the celebration of diversity within society.

"If I hadn't done it, I think I would have probably been locked up. I didn't realise at the time, but working towards something positive kept me sane and gave me a purpose and a meaning in my life when all seemed lost. I think we will see that in America - people banding together for the common good," he said.