(CNN)Occasionally, amidst the cacophony of rescuers yelling orders and the sound of raw concrete and stone being pushed aside, someone will raise a fist.
In the aftermath of an earthquake, silence can save lives
The scene falls silent, and others raise their hands in turn, signaling the unspoken command.
Be quiet. A life could be in the balance.
In and around Mexico City, authorities and rescue workers are asking for complete silence as they search for signs of life following Tuesday's devastating earthquake.
Silence is a precious commodity in these times. Silence is what allows rescue workers to hear a cry for help, or even the faintest breath under the debris.
The gesture, which may not be commonly understood, is gaining steam on social media as people share its meaning.
#PuñosArriba, or "fists up," has become a trend, often attached to pictures of rescuers and volunteers making the gesture during their work.
And while it has a practical significance, the raised first is also serving as a symbol: Of hope, that a life may be found. Of victory, when it is. Of solidarity, as the nation comes together to mourn.
#PuñosArriba significa silencio.
"Fists up means silence," one user wrote on Twitter.
Pero también significa tenemos fuerza y seguimos de pie.
"But it also means that we have strength, and are still standing."