Cardiff Earthquake

The Cardiff Earthquake was the public name that UNIT gave (PROSE: Cardiff Earthquake) to the earthquake caused by Blon Fel-Fotch Passameer-Day Slitheen's plan to trick the Ninth Doctor and Jack Harkness to use the tribophysical waveform macro-kinetic extrapolator to refuel the TARDIS, which actually opened the Cardiff Space-Time Rift instead. (TV: Boom Town)

Background
Seeking to make a profit, a branch of the criminal Slitheen family of Raxacoricofallapatorius came to Earth, where they infiltrated the British government. In March 2006, the Slitheen staged the crash of an alien ship in central London, fabricating an alien invasion so that the United Nations would grant the British government the codes for nuclear weapons which the Slitheen would then use to start World War III, reducing the Earth to radioactive chunks which could be sold as fuel for spacecraft. This plot was opposed by the Ninth Doctor and his companion Rose Tyler, with assistance from Harriet Jones, Mickey Smith, and Jackie Tyler. Ultimately, Mickey, on the Doctor's orders, hacked into the UNIT website and launched a harpoon missile designated UGM-84A at 10 Downing Street, killing the Slitheen (TV: Aliens of London/World War Three) bar one, Blon Fel-Fotch Passameer-Day Slitheen, who used a teleport to escape, ending up on a skip in the Isle of Dogs. (TV: Boom Town)

A Slitheen's Sinister Scheme
Blon made her way to Cardiff, where she managed to get herself elected Lord Mayor of Cardiff. (TV: Boom Town) Her predecessor, Barry Jackson, had killed the former mayor and blamed it on the Auton invasion. (AUDIO: One Rule)

Blon had easily won the mayoral election thanks to low-voter turnout, describing herself as the perfect example of what happened when the people of Cardiff did not make use of their right to vote. In an attempt to leave Earth, she inspected a crashed Illyrian spaceship and met Suzie Costello. The two were joined together by bangles and targeted by missiles, leading them to team up to locate the pilot to save themselves. They succeeded and reached a stalemate with Blon being aware of Suzie breaking Torchwood's rules and Suzie being aware of Blon's identity. The two parted. (AUDIO: Sync)

Secretly, Blon planned to take advantage of the space-time rift located there and advocated a plan for a proposed nuclear power plant called Blaidd Drwg. She wanted to cause an "accident" at Blaidd Drwg. This disaster, located so near the rift, would destroy Earth and provide her tribophysical waveform macro-kinetic extrapolator with sufficient power for her to ride the "surf" into space to escape. She knew that failing this, anyone who arrested her would take the extrapolator for themselves, having "considerable technology of their own" and being "captivated" by the extrapolator. The extrapolator was programmed to lock onto the nearest alien power source and open the rift, still allowing her escape.

She killed anyone who questioned her plans, such as Mr Cleaver. However, in a rare act of mercy, she spared the journalist Cathy Salt after hearing the young woman talk about her family, reminding Blon of her own lost relatives. Soon after, the Ninth Doctor and his companions arrived to stop her; Jack Harkness confiscated the extrapolator and used it to refuel the TARDIS quicker. The Doctor remained uncertain as to what do as she had been sentenced to death on her homeworld in absentia; Blon pleaded the Doctor for mercy and clemency. When the extrapolator began opening the rift through the TARDIS, Blon, threatening Rose, demanded Jack to place the extrapolator at her feet. The extrapolator nearly pulled apart the TARDIS, but the heart of the TARDIS was forced open and Blon looked directly into its light; she was regressed backward along her timeline to the form of an egg. (TV: Boom Town)

Aftermath
With Blon reduced to an egg, the Doctor intended to drop her off at a hatchery on Raxacoricofallapatorius, where she could have a second chance at life. (TV: Boom Town) Adopted by the Jingatheen family, Blon was reborn as Margaret Ag-Kris Therur-Ford Jingatheen, who eventually became a Detective Inspector with the Shadow Proclamation. Left with her human skin suit, Margaret would wear it throughout her life. During her career with the Shadow Proclamation, she led a ship of Judoon, encountered the Twelfth Doctor and faced Weeping Angels. (COMIC: A Confusion of Angels)

UNIT issued a press briefing on 8 October, in the aftermath of the quake, where they announced that the clean-up of the tremor had been successful, however they stated that many people were missing, including Margaret Blaine, and that the Blaidd Drwg Power Plant project would have to be abandoned due to the ground it was to be built on being unstable. (PROSE: Cardiff Earthquake) Torchwood Cardiff, led by an older version of Jack, kept a newspaper clipping of Margaret Blaine as the new Mayor of Cardiff. (TV: Reset) Torchwood also made use of an invisible lift which, as Jack recalled, was enabled when a dimensionally transcendental chameleon circuit placed on a particular spot on Roald Dahl Plass welded its perception properties to the rift. (TV: Everything Changes)

For the TARDIS crew, they moved on from Raxacoricofallapatorious to Kyoto in 1336 before they were brought to the Game Station, where they were embroiled in the Dalek invasion of Earth in the year 200,100. (TV: Bad Wolf) By using Blon's extrapolator, the TARDIS wielded a force field which protected it from the firepower of both the Daleks and their flagship, allowing the Doctor and Jack to rescue Rose when she was captured by them. When the Doctor sent Rose home for her own safety, Rose refused to leave him and, having witnessed the heart of the TARDIS reveal itself before, enlisted Mickey and Jackie's aid to do it again so she could return. Exposed to the energy of the Time Vortex, Rose briefly became the Bad Wolf, the power of which she used to destroy the Dalek Emperor and his fleet whilst resurrecting the slain Captain Jack. However, Rose was endangered by the vortex energy, forcing the Doctor to take it within himself before returning it, resulting in his regeneration into the Tenth Doctor. (TV: The Parting of the Ways)

Much later from the Doctor's perspective, when he took the TARDIS back to Cardiff to refuel again in 2008, Martha Jones recalled the earthquake from a "couple of years ago", correctly presuming that the Doctor was involved. The Doctor admitted that there was a "bit of trouble with the Slitheen" and that he was "a different man back then". (TV: Utopia)

Behind the scenes
The online game Slitheen Surfer depicted an alternate outcome of the events of Boom Town, the objective of the game being to navigate Blon on her extrapolator through the debris of the Earth.