The quake struck at 12:53 GMT with an epicenter 19.3km (12 miles) southeast of the city of Matias Romero, in the state of Oaxaca, the US Geological Survey reported.
Cruz belongs to a social collective and said that when the shaking began, she was riding in a truck carrying supplies to victims of the earlier quake.
At some Mexico City sites rescue workers were still discussing whether to return to their task of trying to reach survivors of Tuesday's quake believe to be buried under debris in three sites in the city.
"I had to get out alive for her", he said. Then the trapped woman had a great stroke of luck: a series of short messages she had written and sent to her husband some 16 hours earlier lit up his phone screen.
On Thursday, they were hard at work, shoveling bricks and concrete from a collapsed house into one of the waiting trucks. He ran to an emergency stairwell, but the floors came down like dominoes, he said. In her words, "I think what kills us most is the desperation of not knowing anything".
As of 21 September, Mexican Civil Protection reports 273 dead but the numbers are expected to rise as search and rescue efforts continue.
As rescue operations stretched into Day 5, residents throughout the capital have held out hope that dozens still missing might be found alive.
All along the highway running south from Mexico City into quake-stricken Morelos state, where at least 73 people died, convoys of volunteers can be seen driving cars decorated with handwritten signs saying "viveros" and "acopio movil", bringing aid and donations to damaged communities.
The Israel Defense Force (IDF) military aid delegation received a warm welcome in Mexico where they are supporting victims of a deadly 7.1 magnitude natural disaster that rocked the Latin American nation on Tuesday.
They weren't public authorities or professionals. On Friday morning, after hours of inactivity blamed on rain, rescuers were readying to re-enter the site, joined by teams from Japan and Israel.
It's the moments between those bits of information that torment the families.
"They couldn't hear us, but we heard them clearly, like if they were just across a window", Mendez said.
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