This fruit's major strength is that it allows the user to generate massive vibrations, or shock waves, which can travel though virtually any medium, including the ground, the seafloor, or even in the air. Because of this, Fleet AdmiralSengoku has stated that Whitebeard holds the power to destroy the world. However, though incredibly powerful, whether it possesses the might to actually destroy the world has yet to be proven.
Sengoku's claim may have referred to the after effects of the fruit, as they may indeed have "the power to destroy the world". It should also be noted that Vice-AdmiralTsuru stated that, even if she retreated to the ends of the ocean, there would be no safe place left in the world. Both Sengoku and Tsuru are renowned as great tacticians, so it is very unlikely that they exaggerated their claims and they truly do believe the Gura Gura no Mi holds the power to destroy the world.
The fruit is capable of devastating an entire island with ease, although its limitations are noticeable: it took repeated usages to come close to destroying the Marine base at Marineford (in fact, Whitebeard failed to do so before dying, and Blackbeard almost completed the task); the shock waves were blocked by the siege wall (albeit it was made from an especially strong metal superior to ordinary steel or kairoseki), and Admiral Aokiji was capable of stopping the tsunami. It should be noted, however, that only after Ace's death did Whitebeard truly attempt to erase Marineford in his anger, but it was Teach who truly was willing to destroy the island using both of his Devil Fruit powers. Although neither men succeeded in sinking the island (having both been stopped and the latter lacking enough control over the power), the resulting aftershocks and tsunami were felt far away from Marineford.
When Blackbeard took this Devil Fruit's power through an unknown method, he claimed that with the power of quakes which "brings destruction to all" combined with the darkness that "reduces anything to nothingness", he was truly invincible and the strongest.
This Devil Fruit's powers are most noted to be a hazard to both friend and foe alike, as observed by both the Whitebeard and Blackbeard Pirates. This is largely because, although the user seems to be able to control both the magnitude of the shock wave and its point of impact, the quakes produced by these shock waves are indiscriminate in their effects. Because of this, allies of the user must be prepared for the impacts unless they want to become unintended victims of them.
This Devil Fruit has no apparent weakness, aside from the standard Devil Fruit weakness. However, the three Admirals were able to stop Whitebeard's shock waves from affecting Marineford's execution platform, possibly by combining their Busoshoku Haki. Also, the siege wall that Sengoku planted was composed of a material Whitebeard's shock waves could not shatter. And, as mentioned previously, due to the fact that Whitebeard's attacks were indiscriminate in who they could hit, his allies and crewmates had to fight a certain distance away from him, giving enemies far more room in attacking him.
Whitebeard has so far demonstrated three separate, distinct skills with his Devil Fruit. He was also able to imbue the direct contact techniques with Busoshoku Haki to attack Logia users at close range. All of his attacks are not named in the manga nor anime, but only in the game One Piece: Gigant Battle.
Kaishin (海震,Kaishin?, literally meaning "Seaquake"): Whitebeard literally cracks the air with a punch and sends devastating shock waves through the air in the direction it is facing. These shock waves are able to pass through and damage almost any substance, tearing it apart. If the shock waves are directed into the ground, the result is a devastating earthquake capable of generating huge tsunamis. Because of its enormous offensive power and great speed, this attack makes for a very good defense, able to destroy or disrupt any attack before it hits Whitebeard. He first used it this way to defend against Aokiji'sice-spears.
Gekishin (激震,Gekishin?, literally meaning "Severe Earthquake"): A close range strike of "Kaishin", causing severe damage, as John Giant and Akainu both suffered. The siege walls in Marineford are made of a special material that is able to resist damage and diffuse the power of this attack. The three Marine Admirals were also capable of blocking this attack from reaching the execution platform. Whitebeard was also able to passively summon vibrations around himself, which protected him from being frozen by Aokiji as vibrations cannot be frozen. In the anime it was also used to deflect cannon balls back to their source.
Kabutowari (兜割,Kabutowari?, literally meaning "Helmet Break"): Whitebeard focuses his great power to a single point, otherwise known as a hypocenter (given the appearance of a bubble of sorts), to make a concentrated, explosion-like attack. So far, he has been shown capable of using this attack through both his fist and the blade of his bisento. He first used this technique to defeat the giantVice-AdmiralRonse with a single blow. In the anime, he also demonstrated the ability to stretch out a quake bubble to form a protective barrier capable of blocking bazooka fire. Also in the anime, Whitebeard has shown he can create such bubble on his foot, making a devastating stomp.
Naginata Rasetsu (薙刀羅刹,Naginata Rasetsu?, literally meaning "Halberd Rakshasa"): Whitebeard surrounds his bisento with the same bubble to greatly increase its striking power and range.
Shima Yurashi (島揺らし,Shima Yurashi?, literally meaning "Island Shaking"): Whitebeard "grabs" an entire area, by grabbing the air around him as if it were tangible, and rapidly shifting it. Using this, he was capable of tilting the entire island of Marineford and the sea around it. This technique was capable of destroying buildings and throwing a giant off of his feet.
One Man Army (一騎当千,Ikkitōsen?, kanji read as:"Matchless Warrior" or "Mighty Hero"): Whitebeard swing his bisento, sending waves of vibrations at his opponents. This was first used in One Piece: Pirate Warriors 2. It is one of Whitebeard's special moves and requires one special gauge to perform.
Heaven and Earth (天地鳴動,Tenchi Meidō?, literally:"Heaven and Earth Rumbling"):Whitebeard grabs the air and pulls it downwards. Then once it gets low enough, all of the opponents get tossed into the sky and fall back down. This was first used in One Piece: Pirate Warriors 2. It is one of Whitebeard's special moves and requires two special gauges to perform. It is similar in execution to Shima Yurashi, but doesn't tilt the earth itself. It is also used by Double-Ability Teach, who needs only one special gauge to perform the attack.
This is the first Devil Fruit to be shown to belong to two separate users, having been acquired by Blackbeard after the death of Whitebeard, via an as-of-yet undisclosed method. Furthermore, it now shares a distinction with the Yami Yami no Mi as the first two fruits to be wielded concurrently by the same user.
The Gura Gura no Mi's powers is one of the two aspects that made Whitebeard resemble the Greek God Poseidon, the other being his status as a Yonko, as the emperor of the seas who could cause earthquakes and tsunamis.
The idea of a Devil Fruit that would allow someone to create tsunamis was first brought up when Morgan explained what Devil Fruits are.
The Hasshoken style utilized by the Happo Navy and Chinjao Family are similar to the Kabutowari technique Whitebeard used, surrounding their strikes with vibrations to shatter defenses.