Shaky Town East : STRONG MOTION, <i> By Jonathan Franzen (Farrar, Straus & Giroux: $21.95; 491 pp.)</i>

“Strong Motion” seems for a while like a brilliant chaos. Bit by bit, the chaos settles--never completely; there are awkward and unassimilated knots of it--the brilliant things remain, and the connections among them begin to appear.

It is not always easy to read Franzen. He has a teeming and seemingly unreined imagination. He will try for more than he can achieve; but he tries for, and achieves, more than all but two or three in the successor generation to Pynchon and DeLillo. He may well be one of the successors.

Franzen’s first novel, “The 27th City,” made a cosmos, real and surreal, of the city of St. Louis. Very roughly, against the forces of dehumanization and greed--a sinister, back-lit panorama of crooked politicians and money men emblematic of Franzen’s sense of modern-day America--he set the Gargantuan figure of a woman warrior: a native of India who becomes the city’s reforming police chief.

“Strong Motion” also uses a city as its setting: Boston and its vicinity. Franzen seems to need cities for his mix of gritty particularity and starry universality. And here again, he has a woman warrior, a figure as outsized as the Indian police chief but much more complex, prickly, human and endearing.

The novel moves through a series of small earthquakes that culminate in a devastating one just north of Boston. The unlikeliness of the locale is explained: These earthquakes are artificially produced. A giant chemical corporation has secretly been pumping its noxious wastes down a well it has drilled deep into the earth’s crust.

Tracing the responsibility of this corporate villain are Renee and Louis, a pair of brainy and messed-up innocents. They are a Hansel and Gretel of modern times, except that they are lovers; and also that she is a Harvard geologist and he an unfocused, dangerously saintly whiz-kid.

“Strong Motion” takes place everywhere at once: in the public realm and in the private histories of its characters, above ground and below ground and, at one point, in the mind of a scavenging raccoon which reflects upon its life and finds it moderately good. The public dimension--the tracing and discovery by Renee and Louis of the activities of the Sweeting-Aldren Corp., the family saga behind the corporation’s growth, and the earthquake itself, which kills dozens, levels shakily built areas and causes a vast chemical contamination--is lively and engrossing.

It is here, though, that some of the book’s thinner spots occur. The account of the greedy corporate founders sounds like “Dynasty.” The fact that Louis’ mother, Melanie, is heir to the founder’s fortune--much of the information he gets comes from his amiably detached father--seems too tightly and forcedly contrived.

On the other hand, there are some splendidly imagined episodes. Taking her early alarming data to the local office of the Environmental Protection Agency, Renee encounters its chief. A large, puffy woman known as “The White Rabbit,” she is all weary sympathy and expert stonewalling. The epitome of immured bureaucracy, she likes to play spitball and use water pistols with her staff.

There is a comically chilly sequence in which Renee hires a plane to overfly the Sweeting complex so she can take photographs. She is violently sick. Upon landing, a Sweeting security patrol opens her camera and takes out her film. The pilot--who is in cahoots with them--mockingly hands her back the airsick bag she used. “Here is your barf,” he says. It also contains the film roll she actually shot, and hid.

Renee is a splendid woman. She brings down on herself the wrath of a militant anti-abortion group when she warns on radio that their headquarters stands on precarious landfill and should be vacated. After emerging from an abortion clinic--she had the procedure after she and Louis quarreled--she walks into a protest riot, grabs the microphone from a TV crew and proceeds to interview herself.

She confronts the group’s leader, the Rev. Stites, and they have a heated discussion. But Franzen is not after simplicities. Stites is a turbulent fanatic, but he is also an idealist and formidably intelligent.

Arrestingly, he gets the better of the argument; Renee is reduced to asking if he will sleep with her.

Franzen conveys powerfully both sides of a hard question. He understands how to make a heroine who is also contradictory, uncertain and sometimes plain awful.

The bad times--political corruption, the maneuvers of predatory exploiters, the hysteria of public controversy, the premonitory tremors of an impending disaster--all these are a background for Franzen’s two fearfully imperfect lovers. It is they who are the heart of the book and who fill its somber stage with a lovely human comedy.

Louis is bright and unsettled. He has the makings of a gifted engineer but he holds a routine job on a small radio station, and soon loses that. He is torn by scruples, generosity and a raging intolerance of sham. He quarrels fiercely with his mother, who has inherited a fortune and won’t give him any of it; and with his sister, who whines, and begs, and gets some.

Renee, older and professionally accomplished, has her own shakiness. She is not sure if she likes herself; she struggles with masochistic impulses, and has a penchant for violent sex. Their love affair is an alternate fleeing toward and away from each other. She tries to wean him from his anger; he tries to wean her from her self-doubt.

Franzen writes beautifully for the most part, though sometimes to excess. He goes on and on about such things as seismology and computer theory, and lucidly conveys not only his understanding but his enthusiasm. A few of his characters are cartoonish, particularly his villains; we may think of Zippy.

Others--the erratic Melanie, clutching her money; a Chinese colleague and sometime lover of Renee, whom she bullies--may at first glance also seem cartoonish, or at least unfleshed. In fact, they play an important role. Like the trou normand-- the spoonful of sorbet in the middle of a huge meal--they cool things down. They help restrain a narrative that is often overheated and sometimes threatens to spill in all directions at once.

But it is with the lovers that Franzen does his most extraordinary writing. He never uses an author’s voice to explain them. He rarely lets them explain themselves. Their interior monologues are eruptions or dreams; rarely do they act as connections.

And so we are often at sea. We don’t know what they are up to or what they will do next. Yet this is Franzen’s way of bringing us to them. We experience them as we experience people in real life. No one seems to be in charge, and that can make for hard going. Often, Renee and Louis don’t know themselves. The author doesn’t know them. We don’t. We all learn together, bit by bit.