Tess is seduced, not raped; although, it might as well be called rape due to the many variables that weakened her before succumbing to Alec's selfish desires. On page 45 on the enotes.com etext ofTess of the D'Ubervilles, she is asleep on the ground after Alec has manipulated the situation beyond her strength. She had been up at five a.m. working, then she was out partying late with friends, then she gets into a fight with one of the girls in the group and Alec "saves" her from these troubles. Little does she know that he takes her riding around in circles for longer than is needed for which she gets angry; but, he avoids her wrath by telling her that he's sent toys and a new horse to her family. She starts crying and she is in a vulnerable position being conflicted by her "nice" stalker and physically and mentally weakened by the day. (There is no pitchfork in this scene as mentioned above in other posts. The pitchfork isn't in Alec's hands until page 217 where he sneakily works along side her in disguise for most of the day. He gets upset and leaves her, but he never uses the pitchfork to threaten her.) Hardy doesn't say if Alec wakes Tess up before taking what he wants from her, but the guilt and resentment that Tess clings to throughout the rest of the book and her life proves that she partially consented. She was taken advantage of, but she was innocent and naive and didn't know what hit her until afterwards. She even asks her mother why she didn't warn her about men before she left to work for Alec.
"Nights grow chilly in September. Let me see." He pulled off a light overcoat that he had worn, and put it round her tenderly. "That's it—now you'll feel warmer," he continued. "Now, my pretty, rest there; I shall soon be back again."
Having buttoned the overcoat round her shoulders he plunged into the webs of vapour which by this time formed veils between the trees. She could hear the rustling of the branches as he ascended the adjoining slope, till his movements were no louder than the hopping of a bird, and finally died away. With the setting of the moon the pale light lessened, and Tess became invisible as she fell into reverie upon the leaves where he had left her.
Roaming up and down, round and round, he at length heard a slight movement of the horse close at hand; and the sleeve of his overcoat unexpectedly caught his foot.
"Tess!" said d'Urberville.
There was no answer. The obscurity was now so great that he could see absolutely nothing but a pale nebulousness at his feet, which represented the white muslin figure he had left upon the dead leaves. Everything else was blackness alike. D'Urberville stooped; and heard a gentle regular breathing. He knelt and bent lower, till her breath warmed his face, and in a moment his cheek was in contact with hers. She was sleeping soundly, and upon her eyelashes there lingered tears.
Darkness and silence ruled everywhere around. Above them rose the primeval yews and oaks of The Chase, in which there poised gentle roosting birds in their last nap; and about them stole the hopping rabbits and hares. But, might some say, where was Tess's guardian angel? where was the providence of her simple faith? Perhaps, like that other god of whom the ironical Tishbite spoke, he was talking, or he was pursuing, or he was in a journey, or he was sleeping and not to be awaked.
Why it was that upon this beautiful feminine tissue, sensitive as gossamer, and practically blank as snow as yet, there should have been traced such a coarse pattern as it was doomed to receive; why so often the coarse appropriates the finer thus, the wrong man the woman, the wrong woman the man, many thousand years of analytical philosophy have failed to explain to our sense of order. One may, indeed, admit the possibility of a retribution lurking in the present catastrophe.
"I didn't understand your meaning till it was too late."
"That's what every woman says."
"How can you dare to use such words!" she cried, turning impetuously upon him, her eyes flashing as the latent spirit (of which he was to see more some day) awoke in her. "My God! I could knock you out of the gig! Did it never strike your mind that what every woman says some women may feel?"
"Very well," he said, laughing; "I am sorry to wound you. I did wrong—I admit it." He dropped into some little bitterness as he continued: "Only you needn't be so everlastingly flinging it in my face. I am ready to pay to the uttermost farthing. You know you need not work in the fields or the dairies again. You know you may clothe yourself with the best, instead of in the bald plain way you have lately affected, as if you couldn't get a ribbon more than you earn."
Tess was raped not seduced....she was ASLEEP in the act so she was obviously raped....
It depends which version you read...
An earlier version shows Alec drugging Tess, with a druggists bottle. (see Penguin Classics edition, edited by Tim Dolin)
Later drafts leave it ambiguous. It could have happened either way. If she was raped, the double standard and Angel's judgement are even more unfair since she had no part to play. However, the message I think is ultimately more powerful if you consider that he seduced her, or at least there was an element of consent/sexual attraction on her part. There was for Angel's indiscretion - should a woman not be permitted the same?
The issue of consent is a tricky one though. You can see the rape/seduction event foreshadowed by Alec's 'forcing' Tess to kiss him, or where he persuades her to let him feed her a strawberry. Technically she consents. But the consent was forced. Rape/seduction?
Later in the text though, Tess admits to being dazed by Alec, which suggests perhaps there was an element of attraction on her part.
Read the essay on rape/seduction in the Tess of the D'Urbervilles Casebook for an interesting discussion of the possible angles.