THE EARTHQUAKE THAT laid waste to the city of Izmit near Istanbul in Turkey Tuesday measured a staggering 7.4 on the Richter scale. But that wasn't the only factor that made this a disaster of horrific proportions. The news and the dreadful images from this quake's aftermath -- rows of six-story buildings collapsed on their foundations, hundreds of streets blocked, families scraping helplessly at the rubble covering their relatives, fires raging out of control from a damaged oil refinery -- show just how much worse things can get when man-made circumstance and geographic chance magnify natural catastrophe.

The quake, the worst in Turkey in modern history, struck a highly industrialized region that is also a major population center. Nearly half the country's population lives in the northwestern region around Istanbul; more have poured into the cities from the countryside in recent years, many settling in makeshift but heavily built-up slums around the city that were the scenes of some of the worst carnage. With the human density came heavy dependence on the infrastructure that had largely collapsed yesterday, leaving survivors without clean water, electricity, communications or medical supplies. The largest Turkish newspaper, Hurriyet, said the quake had "stopped the heart of the economy" and predicted huge losses in the automobile, cement and textile industries.

Turkish newspapers the day after the quake blamed the construction industry for shoddy practices -- "Murderers!" ran one headline -- and said builders and the government had failed to curb unsafe behavior even after the example of previous quakes. "Everything -- we need everything," a government official told reporters as casualty estimates climbed to nearly 4,000 dead and 17,000 wounded. Numerous nations yesterday had indicated their willingness to send teams and aid -- including traditionally hostile neighbors such as Greece and even Cyprus. President Clinton made clear the United States would be part of the effort. Locally, the Assembly of Turkish American Associations is spearheading a fund drive. Along with the altruism that comes to the surface at such times, helpers are surely aware of the importance of helping Turkey, a key ally with always volatile politics, keep its balance under this sudden and devastating blow to the very heart of its life and economy.