Costa Rica sits at the edge of two tectonic plates, where the Cocos Plate is sliding beneath the Caribbean Plate along the Middle America Trench. This ongoing movement causes the land in Costa Rica to slowly shift and deform, sometimes leading to earthquakes. To better understand how the ground is moving, we used data from 154 GPS stations across the country, recorded over nine years. By analyzing this data with advanced mathematical methods, we created a detailed map of how the Earth’s surface is deforming in different parts of Costa Rica.

Our results show that most of the compression and sideways (shear) movement is concentrated along the Nicoya and Osa Peninsulas and their nearby inland areas. In contrast, the Central Valley shows slight stretching. We also found signs that a block of the Earth’s crust, called a “sliver,” is moving independently and may extend further inland than previously thought. This movement helps explain the interaction between the larger Caribbean Plate and the smaller Panama microplate.

These findings give scientists a clearer picture of how tectonic forces are shaping Costa Rica and can help improve earthquake hazard assessments for the region.