Banner curved shadow

Shadow below the banner makes it appear curved.

HTML

<h1><strong>USF Health:</strong> To envision and implement the future of health.</h1>

CSS

body {
    margin: 24px;
}

h1 {
    background: #139573;
    border-bottom: 4px solid #fff;
    color: #fff;
    font-family: sans-serif;
    font-size: 24px;
    font-weight: normal;
    line-height: 70px;
    margin: 0;
    position: relative;
    text-align: center;
}
h1 strong {
    font-weight: bold;
}

h1::before {
    background: transparent;
    box-shadow: 0 4px 10px #000;
    border-radius: 800px / 10px;
    bottom: -2px;
    content: "";
    height: 8px;
    left: 2%;
    position: absolute;
    width: 96%;
    z-index: -1;
}