What tragic event occurred on April 15, 1912?

The event that occurred on April 15, 1912, is primarily known for the sinking of the Titanic after it collided with an iceberg during its maiden voyage. This maritime disaster resulted in the tragic loss of over 1,500 lives and highlighted significant safety regulations and practices within the maritime industry. The sinking of the Titanic stands as a pivotal moment in history, influencing not only maritime safety protocols but also capturing public imagination through literature, film, and ongoing discussions about human error, technology, and preparedness.

The other options, while they reference significant events in their own right, do not pertain to the incident specifically associated with April 15, 1912. The Lusitania sinking occurred in 1915, the collision of ships in a harbor would refer to a different, less prominent incident, and the San Francisco earthquake happened in 1906. Therefore, the Titanic's tragic fate remains the sole significant event tied to that specific date.