After a weeklong lull, Elon Musk has sold another $1 billion worth of Tesla Inc. stock, continuing a nearly monthlong selloff that is expected to continue.

According to filingswith the Securities and Exchanges Commission on Thursday, Musk exercised options to buy 2.1 million shares at $6.24 each and immediately sold more than 934,000 of them at prices ranging from $1,058 to $1,112, making about $1.01 billion.

The sale was the first for the Tesla chief executive since Nov. 23, following a flurry of sales in the previous weeks.

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Musk has sold about 10.1 million shares worth about $10.86 billion since Nov. 8, a day after Musk's Twitter poll decided he should sell 10% of his Tesla stake. Some of the stock sales had been put into motion well before the poll was posted.

Assuming Musk intends to sell 10% of his shares, he's more than halfway there. Before the sales began, his 10% stake amounted to about 17 million shares -- so after Thursday's sales, he has about 6.9 million shares to go.